将 x 减到 0 的最小操作数

class Solution {

public:

int minOperations(vector<int>& nums, int x) {

int sum = 0;

for (int e : nums) sum += e;

int target = sum - x;

if (target < 0) return -1;

int ret = -1;

for (int left = 0, right = 0, tmp = 0; right < nums.size(); right++)

{

tmp += nums[right];

while (target < tmp)

tmp -= nums[left++];

if (tmp == target)

ret = max(ret, right - left + 1);

}

if (ret == -1) return -1;

else return nums.size() - ret;

}

};