CP003255 双指针解法

回文字符串可以用双指针算法来做：

#include<bits/stdc++.h>
#define io freopen("in.txt", "r", stdin), freopen("out.txt", "w", stdout)
#define ll long long
#define ull unsigned long long
using namespace std;
// variables setting
string s;
int leftn,rightn;
// functions(others) defining
// the program subject
void program()
{
    getline(cin,s);
    leftn=0,rightn=s.size()-1;
    while(leftn<rightn)
    {
        if(s[leftn]!=s[rightn])
        {
            cout<<"No"<<endl;
            exit(0);
        }
        leftn++;rightn--;
    }
    cout<<"Yes"<<endl;
}
// the main function
int main()
{
    //io;
    program();
    return 0;
}