在 for 循环中 max() function 的最坏情况复杂度是多少？

Question

I have seen the complexity of max() is O(N). While in program snippets(at geeksforgeeks) I had seen the complexity of such following code is O(N). But how's that's possible if inside for loop these is another function of O(N). So the total complextity should be O(N^2). Please explain what's correct and how?

int x(vector<int> nums){
    int tmp;
    for(auto i=0;i<nums.size();i++){
        maximum=max(nums);
        cout<<maximum;
    }
}

Answer 1

Please explain what's correct

The time complexity of the shown function is O(N*N)

and how?

The function with linear complexity is called a linear number of times.

In theory , a compiler could be smart enough to know that max returns the same value and has no side-effects, and in such case would automatically memoize the result which would result in O(N) complexity. But in practice such proof is often too hard for compilers.