[Codility] Lesson 9 - MaxSliceSum

Task discription

A non-empty array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P ≤ Q < N, is called a slice of array A. The sum of a slice (P, Q) is the total of A[P] + A[P+1] + ... + A[Q].

Write a function:

int solution(vector<int> &A);

that, given an array A consisting of N integers, returns the maximum sum of any slice of A.

For example, given array A such that:

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

the function should return 5 because:

• (3, 4) is a slice of A that has sum 4,
• (2, 2) is a slice of A that has sum −6,
• (0, 1) is a slice of A that has sum 5,
• no other slice of A has sum greater than (0, 1).

Write an efficient algorithm for the following assumptions:

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

• each element of array A is an integer within the range [−1,000,000..1,000,000];

• the result will be an integer within the range [−2,147,483,648..2,147,483,647].

  
  

Source code

#include <algorithm>

int solution(vector<int> &A) {
    int n = A.size();
    int d[n];
    d[0] = A[0];
    for(int i=1;i<n;i++) {
        if(A[i]+d[i-1] > A[i]) {
            d[i] = A[i]+d[i-1];
        }
        else {
            d[i] = A[i];
        }
    }
    int max = -2147483648;
    for(int i=0;i<n;i++) {
        if(d[i] > max) max = d[i];
    }
    return max;
}