Test results - Codility

Tasks Details

medium

1. MaxDoubleSliceSum

Find the maximal sum of any double slice.

Task Score

100%

Correctness

100%

Performance

100%

A non-empty array A consisting of N integers is given.

A triplet (X, Y, Z), such that 0 ≤ X < Y < Z < N, is called a double slice.

The sum of double slice (X, Y, Z) is the total of A[X + 1] + A[X + 2] + ... + A[Y − 1] + A[Y + 1] + A[Y + 2] + ... + A[Z − 1].

For example, array A such that:

A[0] = 3 A[1] = 2 A[2] = 6 A[3] = -1 A[4] = 4 A[5] = 5 A[6] = -1 A[7] = 2

contains the following example double slices:

double slice (0, 3, 6), sum is 2 + 6 + 4 + 5 = 17,

double slice (0, 3, 7), sum is 2 + 6 + 4 + 5 − 1 = 16,

double slice (3, 4, 5), sum is 0.

The goal is to find the maximal sum of any double slice.

Write a function:

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

that, given a non-empty array A consisting of N integers, returns the maximal sum of any double slice.

For example, given:

A[0] = 3 A[1] = 2 A[2] = 6 A[3] = -1 A[4] = 4 A[5] = 5 A[6] = -1 A[7] = 2

the function should return 17, because no double slice of array A has a sum of greater than 17.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [3..100,000];

each element of array A is an integer within the range [−10,000..10,000].

Solution

Programming language used Java 8

Time spent on task 50 minutes

Notes

not defined yet

Task timeline

Code: 03:52:59 UTC, java, verify, result: Failed

show code in pop-up

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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2, Z = 3; Z < A.length - 1; ++X, ++Y, ++Z ) {            
            maxSum = Math.max(0, maxSum + A[X] + A[Y] + A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 32 expected 17

1.370 s

WRONG ANSWER, got 32 expected 17

Code: 03:53:13 UTC, java, verify, result: Failed

show code in pop-up

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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2, Z = 3; Z < A.length - 1; ++X, ++Y, ++Z ) {            
            maxSum = Math.max(0, A[X] + A[Y] + A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 9 expected 17

1.327 s

WRONG ANSWER, got 9 expected 17

Code: 03:53:40 UTC, java, verify, result: Failed

show code in pop-up

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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2, Z = 3; Z < A.length - 1; ++Z ) {            
            maxSum = Math.max(0, A[X] + A[Y] + A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 13 expected 17

1.341 s

WRONG ANSWER, got 13 expected 17

Code: 03:55:47 UTC, java, verify, result: Failed

show code in pop-up

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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2; Y < A.length - 2; ++Y ) {            
            maxSum = Math.max(0, A[X] + A[Y]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 8 expected 17

1.045 s

WRONG ANSWER, got 8 expected 17

Code: 03:57:04 UTC, java, 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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2; Y < A.length - 2; ++Y ) {            
            maxSum = Math.max(0, A[X] + A[Y]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        maxSum = maxSlice;
        for(int Y = 2, Z = 3; Z < A.length - 1; ++Z ) {            
            maxSum = Math.max(0, maxSum + A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 16 expected 17

0.996 s

WRONG ANSWER, got 16 expected 17

Code: 03:57:55 UTC, java, 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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2; Y < A.length - 2; ++Y ) {            
            maxSum = Math.max(0, A[X] + A[Y]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        maxSum = maxSlice;
        for(int Y = 2, Z = 3; Z < A.length - 1; ++Z ) {            
            maxSum = Math.max(0, maxSum + A[Y] +  A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 39 expected 17

1.341 s

WRONG ANSWER, got 39 expected 17

Code: 03:58:13 UTC, java, 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


class Solution {
    public int solution(int[] A) {
        int maxSum = 0, maxSlice = 0;
        
        for(int X = 1, Y = 2; Y < A.length - 2; ++Y ) {            
            maxSum = Math.max(0, A[X] + A[Y]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        maxSum = maxSlice;
        for(int Y = 2, Z = 3; Z < A.length - 1; ++Z ) {            
            maxSum = Math.max(0, A[Y] + A[Z]);
            maxSlice = Math.max(maxSlice, maxSum);
        }
        
        return maxSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 11 expected 17

1.344 s

WRONG ANSWER, got 11 expected 17

Code: 04:35:23 UTC, java, 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


class Solution {
    public int solution(int[] A) {        
        int[] maxStartingHere = new int[A.length];
        int[] maxEndingHere = new int[A.length];
        int maxSum = 0, len = A.length;
        
        for(int i = len - 2; i > 0; --i ) {            
            maxSum = Math.max(0,maxSum + A[i] + maxSum);
            maxStartingHere[i] = maxSum;
        }
        maxSum = 0;
        for(int i = 1; i < len - 1; ++i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxEndingHere[i] = maxSum;
        }
        int maxDoubleSlice = 0;
        
        for(int i = 0; i < len - 2; ++i) {
            maxDoubleSlice = Math.max(maxDoubleSlice, maxEndingHere[i] + maxStartingHere[i+2]);
        }
        
        return maxDoubleSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✘

WRONG ANSWER
got 60 expected 17

1.339 s

WRONG ANSWER, got 60 expected 17

Code: 04:38:31 UTC, java, 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


class Solution {
    public int solution(int[] A) {        
        int[] maxStartingHere = new int[A.length];
        int[] maxEndingHere = new int[A.length];
        int maxSum = 0, len = A.length;
        
        for(int i = len - 2; i > 0; --i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxStartingHere[i] = maxSum;
        }
        maxSum = 0;
        for(int i = 1; i < len - 1; ++i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxEndingHere[i] = maxSum;
        }
        int maxDoubleSlice = 0;
        
        for(int i = 0; i < len - 2; ++i) {
            maxDoubleSlice = Math.max(maxDoubleSlice, maxEndingHere[i] + maxStartingHere[i+2]);
        }
        
        return maxDoubleSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✔

1.396 s

Code: 04:38:56 UTC, java, 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


class Solution {
    public int solution(int[] A) {        
        int[] maxStartingHere = new int[A.length];
        int[] maxEndingHere = new int[A.length];
        int maxSum = 0, len = A.length;
        
        for(int i = len - 2; i > 0; --i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxStartingHere[i] = maxSum;
        }
        maxSum = 0;
        for(int i = 1; i < len - 1; ++i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxEndingHere[i] = maxSum;
        }
        int maxDoubleSlice = 0;
        
        for(int i = 0; i < len - 2; ++i) {
            maxDoubleSlice = Math.max(maxDoubleSlice, maxEndingHere[i] + maxStartingHere[i+2]);
        }
        
        return maxDoubleSlice;

    }
}

Analysis

expand all Example tests

▶

example
example test

✔

1.072 s

Code: 04:39:04 UTC, java, final, score: 100

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


class Solution {
    public int solution(int[] A) {        
        int[] maxStartingHere = new int[A.length];
        int[] maxEndingHere = new int[A.length];
        int maxSum = 0, len = A.length;
        
        for(int i = len - 2; i > 0; --i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxStartingHere[i] = maxSum;
        }
        maxSum = 0;
        for(int i = 1; i < len - 1; ++i ) {            
            maxSum = Math.max(0, A[i] + maxSum);
            maxEndingHere[i] = maxSum;
        }
        int maxDoubleSlice = 0;
        
        for(int i = 0; i < len - 2; ++i) {
            maxDoubleSlice = Math.max(maxDoubleSlice, maxEndingHere[i] + maxStartingHere[i+2]);
        }
        
        return maxDoubleSlice;

    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

expand all Example tests

▶

example
example test

✔

1.383 s

expand all Correctness tests

▶

simple1
first simple test

✔

1.367 s

1.356 s

1.373 s

▶

simple2
second simple test

✔

1.382 s

1.373 s

▶

simple3
third simple test

✔

1.372 s

▶

negative
all negative numbers

✔

1.364 s

▶

positive
all positive numbers

✔

1.369 s

▶

extreme_triplet
three elements

✔

1.379 s

expand all Performance tests

▶

small_random1
random, numbers form -10**4 to 10**4, length = 70

✔

1.391 s

▶

small_random2
random, numbers from -30 to 30, length = 300

✔

1.431 s

▶

medium_range
-1000, ..., 1000

✔

1.389 s

▶

large_ones
random numbers from -1 to 1, length = ~100,000

✔

1.530 s

▶

large_random
random, length = ~100,000

✔

1.614 s

▶

extreme_maximal
all maximal values, length = ~100,000

✔

1.642 s

▶

large_sequence
many the same small sequences, length = ~100,000

✔

1.565 s

1.597 s