地址：1664. 生成平衡数组的方案数

    结果：AC

    代码：

    1. class Solution {
    2. public:
    3.     int waysToMakeFair(vector<int>& nums) {
    4.         int l_odd = 0;
    5.         int r_odd = 0;
    6.         int l_even = 0;
    7.         int r_even = 0;
    8.         for (int i = 0; i < nums.size(); i++) {
    9.             if(i%2 == 0) r_even += nums[i];
    10.             else r_odd += nums[i];
    11.         }
    12.         int ans = 0;
    13.         for (int i = 0; i < nums.size(); i++) {
    14.             if(i%2 == 0) {
    15.                 r_even -= nums[i];
    16.                 if(l_even + r_odd == l_odd + r_even) ans++;
    17.                 l_even += nums[i];
    18.             } else {
    19.                 r_odd -= nums[i];
    20.                 if(l_even + r_odd == l_odd + r_even) ans++;
    21.                 l_odd += nums[i];
    22.             }
    23.         }
    24.         return ans;
    25.     }
    26. };