for auto x nums

class Solution {public: int findDuplicate(vector<int>& nums) { int n = nums.size() - 1; int l = 1, r = n; while (l < r){ int mid = l + r >> 1; int cnt = 0; for (auto x : nums) if (x >= l && x <= mid) cnt++; if (cnt > mid - l + 1) r = mid; else l = mid + 1; } return r; }};

上述代码中

for (auto x : nums)

作用就是迭代容器中所有的元素，每一个元素的临时名字就是x，等同于下边代码

for (vector<int>::iterator iter = nums.begin(); iter != nums.end(); iter++)