[leetcode/lintcode 题解] 微软面试题：公平索引

输入: [4,-1,0,3] [-2,5,0,3]
输出: 2

输入: [2,-2,-3,3]
[0,0,4,-4]
输出: 1

输入: [4,-1,0,3] [-2,6,0,4]
输出: 0

输入: [1,4,2,-2,5] [7,-2,-2,2,5]
输出: 2

public class Solution {
    /**
     * @param A: an array of integers
     * @param B: an array of integers
     * @return: return a integer indicating the number of fair indexes.
     */
    public int CountIndexes(List<Integer> A, List<Integer> B) {
        int ans = 0;
        long sum_a = 0, sum_b = 0, pre_a = 0, pre_b = 0;
        for(int i = 0; i < A.size(); i++)
        {
            sum_a += A.get(i);
            sum_b += B.get(i);
        }
        if(sum_a != sum_b)return 0;
        for(int i = 0; i < A.size() - 1; i++)
        {
            pre_a += A.get(i);
            pre_b += B.get(i);
            if(pre_a==pre_b)
                ans++;
        }
        return ans;
    }
}