Test results - Codility

Tasks Details

easy

1. StoneWall

Cover "Manhattan skyline" using the minimum number of rectangles.

Task Score

100%

Correctness

100%

Performance

100%

You are going to build a stone wall. The wall should be straight and N meters long, and its thickness should be constant; however, it should have different heights in different places. The height of the wall is specified by an array H of N positive integers. H[I] is the height of the wall from I to I+1 meters to the right of its left end. In particular, H[0] is the height of the wall's left end and H[N−1] is the height of the wall's right end.

The wall should be built of cuboid stone blocks (that is, all sides of such blocks are rectangular). Your task is to compute the minimum number of blocks needed to build the wall.

Write a function:

class Solution { public int solution(int[] H); }

that, given an array H of N positive integers specifying the height of the wall, returns the minimum number of blocks needed to build it.

For example, given array H containing N = 9 integers:

H[0] = 8 H[1] = 8 H[2] = 5 H[3] = 7 H[4] = 9 H[5] = 8 H[6] = 7 H[7] = 4 H[8] = 8

the function should return 7. The figure shows one possible arrangement of seven blocks.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..100,000];

each element of array H is an integer within the range [1..1,000,000,000].

Solution

Programming language used C#

Time spent on task 32 minutes

Notes

not defined yet

Task timeline

Code: 11:23:33 UTC, cs, verify, result: Failed

show code in pop-up

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using System;
// you can also use other imports, for example:
// using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
        int blocks = H.Length;
        
        (for int=i; i<H.Length-1; I++)
            if (H[i] == H[i+1]) blocks--;
    }
}

Analysis

Compile error

Compilation failed: 4 error(s), 0 warnings
Solution.cs(13,9): error CS1525: Unexpected symbol `for'
Solution.cs(13,13): error CS1525: Unexpected symbol `int'
Solution.cs(13,16): error CS1525: Unexpected symbol `='
Solution.cs(13,37): error CS1525: Unexpected symbol `)', expecting `;' or `}'

Code: 11:23:56 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

using System;
// you can also use other imports, for example:
// using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
        int blocks = H.Length;
        
        for (int=i; i<H.Length-1; I++)
           { if (H[i] == H[i+1]) blocks--; }
        return blocks;
    }
}

Analysis

Compile error

Compilation failed: 2 error(s), 0 warnings
Solution.cs(13,16): error CS1525: Unexpected symbol `='
Solution.cs(13,37): error CS1525: Unexpected symbol `)', expecting `;' or `}'

Code: 11:24:03 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

using System;
// you can also use other imports, for example:
// using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
        int blocks = H.Length;
        
        for (int i=0; i<H.Length-1; I++)
           { if (H[i] == H[i+1]) blocks--; }
        return blocks;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(13,37): error CS0103: The name `I' does not exist in the current context

Code: 11:24:10 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

using System;
// you can also use other imports, for example:
// using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
        int blocks = H.Length;
        
        for (int i=0; i<H.Length-1; i++)
           { if (H[i] == H[i+1]) blocks--; }
        return blocks;
    }
}

Analysis

expand all Example tests

▶

example

✘

WRONG ANSWER
got 8 expected 7

0.060 s

WRONG ANSWER, got 8 expected 7

Code: 11:37:13 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0l i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i] break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}

Analysis

Compile error

Compilation failed: 3 error(s), 1 warnings
Solution.cs(17,20): warning CS0078: The `l' suffix is easily confused with the digit `1' (use `L' for clarity)
Solution.cs(17,22): error CS1525: Unexpected symbol `i'
Solution.cs(17,29): error CS1525: Unexpected symbol `}'
Solution.cs(20,55): error CS1525: Unexpected symbol `break'

Code: 11:37:39 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i] break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(20,55): error CS1525: Unexpected symbol `break'

Code: 11:38:04 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i] continue;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(20,55): error CS1525: Unexpected symbol `continue'

Code: 11:38:17 UTC, cs, verify, result: Failed

show code in pop-up

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using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i] wallNum = wallNum;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(20,55): error CS1525: Unexpected symbol `wallNum'

Code: 11:38:31 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(28,246): error CS1525: Unexpected symbol `end-of-file'

Code: 11:38:45 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}
}

Analysis

Compile error

Compilation failed: 4 error(s), 0 warnings
Solution.cs(14,31): error CS0305: Using the generic type `System.Collections.Generic.Stack<T>' requires `1' type argument(s)
/opt/codility-mono/lib/mono/4.5/System.dll (Location of the symbol related to previous error)
Solution.cs(19,36): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(20,35): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(24,25): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'

Code: 11:39:10 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack<int>();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 & wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}
}

Analysis

Compile error

Compilation failed: 3 error(s), 0 warnings
Solution.cs(19,36): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(20,35): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(24,25): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'

Code: 11:39:20 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        Stack<int> wall = new Stack<int>();
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}
}

Analysis

Compile error

Compilation failed: 3 error(s), 0 warnings
Solution.cs(19,37): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(20,35): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'
Solution.cs(24,25): error CS0021: Cannot apply indexing with [] to an expression of type `System.Collections.Generic.Stack<int>'

Code: 11:42:01 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;            
        }
        return stones;
    }
}
}

Analysis

Compile error

Compilation failed: 1 error(s), 1 warnings
Solution.cs(9,16): error CS0161: `Solution.solution(int[])': not all code paths return a value
Solution.cs(17,28): warning CS0162: Unreachable code detected

Code: 11:42:38 UTC, cs, verify, result: Failed

show code in pop-up

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using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;     
                }
        }
        return stones;
    }
}
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(31,0): error CS1525: Unexpected symbol `}'

Code: 11:42:51 UTC, cs, verify, result: Failed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) break;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;     
                }
        }
        return stones;
    }

}

Analysis

expand all Example tests

▶

example

✘

WRONG ANSWER
got 1 expected 7

0.055 s

WRONG ANSWER, got 1 expected 7

Code: 11:43:07 UTC, cs, verify, result: Passed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) continue;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;     
                }
        }
        return stones;
    }

}

Analysis

expand all Example tests

▶

example

✔

0.054 s

Code: 11:43:14 UTC, cs, verify, result: Passed

show code in pop-up

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using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) continue;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;     
                }
        }
        return stones;
    }

}

Analysis

expand all Example tests

▶

example

✔

0.054 s

Code: 11:43:19 UTC, cs, final, score: 100

show code in pop-up

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using System;
// you can also use other imports, for example:
using System.Collections.Generic;

// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");

class Solution {
    public int solution(int[] H) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
      
        int L = H.Length;
        int stones =0;
        int [] wall = new int [L];
        int wallNum=0;
        
        for (int i=0; i<L; i++)
        {
            while (wallNum>0 && wall[wallNum-1] > H[i]) wallNum -=1;   
            if (wallNum >0 && wall[wallNum -1] == H[i]) continue;
            else 
                {
                    stones +=1;
                    wall[wallNum] = H[i];
                    wallNum +=1;     
                }
        }
        return stones;
    }

}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example

✔

0.062 s

expand all Correctness tests

▶

simple1

✔

0.061 s

▶

simple2

✔

0.061 s

▶

simple3

✔

0.061 s

▶

simple4

✔

0.061 s

0.060 s

▶

boundary_cases

✔

0.061 s

expand all Performance tests

▶

medium1

✔

0.061 s

▶

medium2

✔

0.061 s

▶

medium3

✔

0.061 s

▶

medium4

✔

0.061 s

▶

large_piramid

✔

0.096 s

▶

large_increasing_decreasing

✔

0.097 s

▶

large_up_to_20

✔

0.089 s

▶

large_up_to_100

✔

0.090 s

▶

large_max

✔

0.113 s