Task description
A non-empty zero-indexed 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 zero-indexed 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.
Assume that:
- 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].
Complexity:
- expected worst-case time complexity is O(N);
- expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).
Elements of input arrays can be modified.
Solution
Programming language used: Java
Code: 00:31:25 UTC, java, final, score: 100
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// you can also use imports, for example:
// import java.util.*;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
import java.lang.Math;
class Solution {
public int solution(int[] A) {
// write your code in Java SE 8
if(A.length < 4)
return 0;
int maxleft=0, maxending=0, maxslice=0;
for(int i=3; i<A.length; i++) {
maxleft = Math.max(maxleft+A[i-2], A[i-2]);
maxending = Math.max(maxleft, Math.max( A[i-1], maxending+A[i-1]));
maxslice = Math.max(maxending, maxslice);
}
return maxslice;
}
}
https://codility.com/demo/results/trainingEJXAE5-H5P/