回文串----蘑菇街2016校园招聘

题目描述：给一个字符串，能否通过添加一个字符使其变成一个回文字符串，如果能，输出YES,不能，输出NO。

样例输入：coco

样例输出：YES

CODE:

#include <iostream>
#include <string>
using namespace std;
bool is_p(string s)
{
    int len = s.length();
    if (len < 2) return true;
    for (int i = 0; i < len / 2; ++i)
    {
        int j = len - i - 1;
        if (s[i] != s[j])
            return false;
    }
    return true;
}
string reverse(string str)
{
    int len = str.length();
    for (int i = 0; i < len / 2; ++i)
    {
        int j = len - i - 1;
        char t = str[i];
        str[i] = str[j];
        str[j] = t;
    }
    return str;
}
bool judge(string str, int middle)
{
    int len = str.length();
    for (int i = 0; i < middle; i++)
    {
        int j = len - i - 1;
        if (str[i] != str[j])
        {
            str.insert(j+1, 1, str[i]);  //注意：j+1
            break;
        }
    }
    if (is_p(str))
        return true;
    else return false;
}
int main()
{
    string str;
    while (cin >> str)
    {
        if (is_p(str) || str.length() < 3)
        {
            cout << "YES" << endl;
            continue;
        }
        int len = str.length();
        if (judge(str, len / 2 + 1))
        {
            cout << "YES" << endl;
            continue;
        }
        if (judge(reverse(str), len / 2 + 1))
        {
            cout << "YES" << endl;
            continue;
        }
        cout << "NO" << endl;
    }
}