ZJUT OJ 1031

对称串 
Time Limit:1000MS  Memory Limit:32768K

Description:

有一些字串，有些对称，有些不对称，请将对称的串按长度排列。

Sample Input:

123321
123454321
123
321
sdfsdfd
121212
\\dd\\

Sample Output:

123321
\\dd\\
123454321

code ：

/*

*/
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

struct cmp
{
    public:
        bool operator () (const string &s1, const string &s2) {
            return s1.length() < s2.length();
        }
};
bool is_symmetrical (string str);

int main()
{
    vector<string> ve;
    for (string str; cin >> str;) {
        if (is_symmetrical(str))
            ve.push_back(str);
    }
    if (ve.size()) {
        sort(ve.begin(), ve.end(), cmp());
        int i = 0, len = ve.size();
        for (; i < len; i++)
            cout << ve[i] << endl;
    }
}

bool is_symmetrical (string str) {
    bool symmetry = true;
    int len  = str.length(), i = 0;
    for (; i < len / 2; i++) {
        if (str[i] != str[len - i - 1])
            symmetry = false;
    }
    return symmetry;
}