Test results - Codility

Tasks Details

medium

1. NumberOfDiscIntersections

Compute the number of intersections in a sequence of discs.

Task Score

93%

Correctness

87%

Performance

100%

We draw N discs on a plane. The discs are numbered from 0 to N − 1. An array A of N non-negative integers, specifying the radiuses of the discs, is given. The J-th disc is drawn with its center at (J, 0) and radius A[J].

We say that the J-th disc and K-th disc intersect if J ≠ K and the J-th and K-th discs have at least one common point (assuming that the discs contain their borders).

The figure below shows discs drawn for N = 6 and A as follows:

A[0] = 1 A[1] = 5 A[2] = 2 A[3] = 1 A[4] = 4 A[5] = 0

There are eleven (unordered) pairs of discs that intersect, namely:

discs 1 and 4 intersect, and both intersect with all the other discs;

disc 2 also intersects with discs 0 and 3.

Write a function:

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

that, given an array A describing N discs as explained above, returns the number of (unordered) pairs of intersecting discs. The function should return −1 if the number of intersecting pairs exceeds 10,000,000.

Given array A shown above, the function should return 11, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000];

each element of array A is an integer within the range [0..2,147,483,647].

Solution

Programming language used C#

Time spent on task 9 minutes

Notes

not defined yet

Task timeline

Code: 11:32:28 UTC, cs, verify, result: Passed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            int result = 0;
    int[] dps = new int[A.Length];
    int[] dpe = new int[A.Length];

    for (int i = 0; i < A.Length; i++)
    {
        dps[Math.Max(0, i - A[i])]++;
        dpe[Math.Min(A.Length - 1, i + A[i])]++;
    }

    int t = 0;
    for (int i = 0; i < A.Length; i++)
    {
        if (dps[i] > 0)
        {
            result += t * dps[i] + dps[i] * (dps[i] - 1) / 2;
            
            t += dps[i];
        }
        t -= dpe[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.060 s

Code: 11:35:19 UTC, cs, verify, result: Failed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Lenght;
    int[] AX = new int[A.Length];
    int[] AY = new int[A.Length];

    for (int i = 0; i < N; i++)
    {
        dps[Math.Max(0, i - A[i])]++;
        dpe[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAti = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAti * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAti += AX[i];
        }
        discsAti -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

Compile error

Compilation failed: 3 error(s), 0 warnings
Solution.cs(12,15): error CS1061: Type `int[]' does not contain a definition for `Lenght' and no extension method `Lenght' of type `int[]' could be found. Are you missing an assembly reference?
/opt/codility-mono/lib/mono/4.5/mscorlib.dll (Location of the symbol related to previous error)
Solution.cs(18,9): error CS0103: The name `dps' does not exist in the current context
Solution.cs(19,9): error CS0103: The name `dpe' does not exist in the current context

Code: 11:35:34 UTC, cs, verify, result: Failed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Lenght;
    int[] AX = new int[A.Length];
    int[] AY = new int[A.Length];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAti = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAti * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAti += AX[i];
        }
        discsAti -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

Compile error

Compilation failed: 1 error(s), 0 warnings
Solution.cs(12,15): error CS1061: Type `int[]' does not contain a definition for `Lenght' and no extension method `Lenght' of type `int[]' could be found. Are you missing an assembly reference?
/opt/codility-mono/lib/mono/4.5/mscorlib.dll (Location of the symbol related to previous error)

Code: 11:36:16 UTC, cs, verify, result: Passed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    int[] AX = new int[N];
    int[] AY = new int[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAti = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAti * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAti += AX[i];
        }
        discsAti -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.060 s

Code: 11:36:18 UTC, cs, verify, result: Passed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    int[] AX = new int[N];
    int[] AY = new int[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAti = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAti * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAti += AX[i];
        }
        discsAti -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.062 s

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

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    int[] AX = new int[N];
    int[] AY = new int[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.066 s

Code: 11:38:55 UTC, cs, verify, result: Failed

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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 32 33 34 35 36 37

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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    long [] AX = new int[N];
    long [] AY = new int[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    int result = 0;
    int discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return result;
    else return -1;
    }
}

Analysis

Compile error

Compilation failed: 5 error(s), 0 warnings
Solution.cs(13,18): error CS0029: Cannot implicitly convert type `int[]' to `long[]'
Solution.cs(14,18): error CS0029: Cannot implicitly convert type `int[]' to `long[]'
Solution.cs(27,23): error CS0266: Cannot implicitly convert type `long' to `int'. An explicit conversion exists (are you missing a cast?)
Solution.cs(29,31): error CS0266: Cannot implicitly convert type `long' to `int'. An explicit conversion exists (are you missing a cast?)
Solution.cs(31,27): error CS0266: Cannot implicitly convert type `long' to `int'. An explicit conversion exists (are you missing a cast?)

Code: 11:39:41 UTC, cs, verify, result: Failed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    long [] AX = new int[N];
    long [] AY = new int[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    long result = 0;
    long discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return (int) result;
    else return -1;
    }
}

Analysis

Compile error

Compilation failed: 2 error(s), 0 warnings
Solution.cs(13,18): error CS0029: Cannot implicitly convert type `int[]' to `long[]'
Solution.cs(14,18): error CS0029: Cannot implicitly convert type `int[]' to `long[]'

Code: 11:39:57 UTC, cs, verify, result: Passed

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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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    long [] AX = new long[N];
    long [] AY = new long[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    long result = 0;
    long discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return (int) result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.061 s

Code: 11:40:15 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 32 33 34 35 36 37

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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    long [] AX = new long[N];
    long [] AY = new long[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    long result = 0;
    long discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return (int) result;
    else return -1;
    }
}

Analysis

expand all Example tests

▶

example1
example test

✔

0.064 s

Code: 11:40:17 UTC, cs, final, score: 93

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 32 33 34 35 36 37

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[] A) {
        // write your code in C# 6.0 with .NET 4.5 (Mono)
            
    int N = A.Length;
    long [] AX = new long[N];
    long [] AY = new long[N];

    for (int i = 0; i < N; i++)
    {
        AX[Math.Max(0, i - A[i])]++;
        AY[Math.Min(N-1, i + A[i])]++;
    }
    long result = 0;
    long discsAtIndex = 0;
    for (int i = 0; i <N; i++)
    {
        if (AX[i] > 0)
        {
            result += discsAtIndex * AX[i] + (AX[i] * (AX[i] - 1) / 2);
            
            discsAtIndex += AX[i];
        }
        discsAtIndex -= AY[i];
    }
    if (result <= 10000000)
     return (int) result;
    else return -1;
    }
}

Analysis summary

The following issues have been detected: runtime errors.

Analysis

Detected time complexity:

O(N*log(N)) or O(N)

expand all Example tests

▶

example1
example test

✔

0.060 s

expand all Correctness tests

▶

simple1

✔

0.059 s

▶

simple2

✔

0.060 s

0.059 s

▶

simple3

✔

0.059 s

▶

extreme_small
empty and [10]

✔

0.059 s

▶

small1

✔

0.059 s

▶

small2

✔

0.059 s

▶

small3

✔

0.059 s

▶

overflow
arithmetic overflow tests

✘

RUNTIME ERROR
tested program terminated unexpectedly

0.055 s

RUNTIME ERROR, tested program terminated unexpectedly

stderr:

Unhandled Exception:
System.IndexOutOfRangeException: Array index is out of range.
  at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException: Array index is out of range.
  at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0

0.054 s

RUNTIME ERROR, tested program terminated unexpectedly

stderr:

Unhandled Exception:
System.IndexOutOfRangeException: Array index is out of range.
  at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException: Array index is out of range.
  at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 
  at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0

expand all Performance tests

▶

medium1

✔

0.060 s

▶

medium2

✔

0.060 s

▶

medium3

✔

0.062 s

▶

medium4

✔

0.062 s

▶

10M_intersections
10.000.000 intersections

✔

0.066 s

▶

big1

✔

0.086 s

0.061 s

▶

big2

✔

0.076 s

0.060 s

▶

big3
[0]*50000

✔

0.072 s

0.060 s