MaxSliceSum.go

package max_slice

import "math"

/*
A non-empty zero-indexed 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:

func Solution(A []int) int
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).
Assume that:

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].
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).
 */

func MaxSliceSum(A []int) int {
	maxSum := float64(1 - (1 << 32 - 1))
	maxEnding := maxSum

	for _, value := range (A) {
		maxEnding = math.Max(float64(value), float64(value) + maxEnding)
		maxSum = math.Max(maxEnding, maxSum)
	}

	return int(maxSum)
}