在这里我使用内置的 stl max 函数，但它不起作用[重复]

Question

int maxDepth(string s) {
    stack<char>st;
    int ans=0;
    for(char ch:s){
        if(ch=='('){
            st.push('(');
            ans=max(ans,st.size());
        } else if(ch==')') st.pop();
    }
    return ans;
}

它显示

Line 9: Char 21: error: no matching function for call to 'max'
                ans=max(ans,st.size());
                    ^~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/algorithmfwd.h:370:5: note: candidate template ignored: deduced conflicting types for parameter '_Tp' ('int' vs. 'unsigned long')
    max(const _Tp&, const _Tp&);
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/stl_algo.h:3462:5: note: candidate template ignored: could not match 'initializer_list<type-parameter-0-0>' against 'int'
    max(initializer_list<_Tp> __l, _Compare __comp)
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/stl_algo.h:3456:5: note: candidate function template not viable: requires single argument '__l', but 2 arguments were provided
    max(initializer_list<_Tp> __l)
    ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/algorithmfwd.h:375:5: note: candidate function template not viable: requires 3 arguments, but 2 were provided
    max(const _Tp&, const _Tp&, _Compare);
    ^
1 error generated.

Answer 1

int maxDepth(string s) {
    stack<char>st;
    //int ans=0; <<< this is signed but stack size is unsigned change it to 
    size_t ans=0;
    for(char ch:s){
        if(ch=='('){
            st.push('(');
            ans=max(ans,st.size()); //<<< you cant do max with different types
        } else if(ch==')') st.pop();
    }
    return ans;
}