FastPrep
Problem · Array

Find Fair Indexes

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Problem statement

You are given two arrays A and B consisting of N integers each.

Index K is named fair if the four sums A[0]+...A[K-1]), A[K]+...+A[N-1]), B[0]+...+B[K-1]) and B[K]+...+B[N-1]) are all equal. In other words, K is the index where the two arrays, A and B, can be split (into two non-empty arrays each) in such a way that the sums of the resulting arrays' elements are equal.

For example, given arrays A = [4,-1, 0, 3] and B = [-2, 5, 0, 3], index K = 2 is fair. The sums of the subarrays are all equal: 4+(-1) = 3; 0+3 = 3; -2 + 5 = 3 and 0 + 3 = 3.

Function

findFairIndex(A: int[], B: int[]) → int

Examples

Example 1

A = [4,-1,0,3]B = [-2,5,0,3]return = 2
Index K = 2 is fair. The sums of the subarrays are all equal: 4+(-1) = 3; 0+3 = 3; -2 + 5 = 3 and 0 + 3 = 3.

Example 2

A = [2,-2,-3,3]B = [0,0,4,-4]return = 1
Index K = 1 is fair. The sums of the subarrays are all equal: 2 = 2; -2+(-3)+3 = 0; 0 = 0; 0+4+(-4) = 0.

Example 3

A = [4,-1,0,3]B = [-2,6,0,4]return = 0
There is no fair index K in this case.

Example 4

A = [1,4,2,-2,5]B = [7,-2,-2,2,5]return = 2
Index K = 2 is fair. The sums of the subarrays are all equal: 1+4 = 5; 2+(-2)+5 = 5; 7+(-2) = 5; (-2)+2+5 = 5.

Constraints

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public int findFairIndex(int[] A, int[] B) {
  // write your code here
}
A[4,-1,0,3]
B[-2,5,0,3]
expected2
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