1.判断回文字符串

#include<iostream>

using namespace std;

bool f(string str,int l,int r){
    if(l == (str.size() / 2))//if(r == (str.size() / 2) - 1) 这两种写法都能过
        return true;
    else{
        char c1 = str[l],c2 = str[r];
        if(c1 == c2)
            return f(str,l + 1,r - 1);
        else 
            return false;
    }
}

int main()
{
    string s;
    while(cin >> s){
        bool f = true;
        int n = s.size();
        for(int i = 0,j = n - 1;i <= n/2;i ++,j --){
            if(s[i] != s[j]){
                f = false;
                break;
            }
        }
        if(f) cout << "Yes!" << endl;
        else cout << "No!" << endl;
    }
}