Find the Middle Index in Array

定义middleindex是一个index的左右两边的sum都一样(不包含自己), 找到最左边的middle index.

这题就是做下presum, 然后找.

class Solution {
    public int findMiddleIndex(int[] nums) {
        int rightSum = 0;
        for(int i = 1; i < nums.length; i++)
            rightSum += nums[i];
        int leftSum = 0;
        for(int i = 0; i < nums.length; i++){
            if(leftSum == rightSum)
                return i;
            leftSum += nums[i];
            if(i < nums.length - 1)
                rightSum -= nums[i + 1];
        }
        return -1;
    }
}