LeetCode-5_Longest Palindrome Substring

/*
 * main.cpp
 *
 *  Created on: 2017年10月16日
 *      Author: zhy
 *
 *      Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.
 *      Example:
 *      Input: "babad"
 *      Output: "bab"
 *      Note: "aba" is also a valid answer.
 *      Example:
 *      Input: "cbbd"
 *      Output: "bb"
 */

#include <iostream>
#include <hash_map>

using namespace std;
using namespace __gnu_cxx;

class Solution {
public:
    static const string longestPalindrome(const string& s)
    {
        //Brute Force暴力穷举法
        std::size_t length = s.size();
        int longestPalindromeLength = 0;
        string ret("");
        for(int i = 0;i < length;++i){
            for(int j = i+1;j <= length;++j){       //下面使用迭代器来构造string,由于这种构造方法中的迭代器区间是左闭右开的，因此for()条件带上等号
                string tmpStr(s.begin()+i,s.begin()+j);
                if(true == Solution::isPalindrome(tmpStr)){
                    if(tmpStr.size() > longestPalindromeLength){
                        ret = tmpStr;
                        longestPalindromeLength = tmpStr.size();
                    }
                }
            }
        }
        return ret;
    }

    /*判断参数string是否为回文
        可以用于得到一个string内的substring组成的所有回文*/
    static bool isPalindrome(const string& s)
    {
        std::size_t length = s.size();
        if(length == 0)
            return false;
        int left = 0;
        int right = length-1;
        for(;left <= right;left++,right--){
            if(s[left] != s[right]){
                return false;
            }
        }
        return true;
    }
};

int main(int argc,char *argv[])
{
    string s("babad");
    auto ret = Solution::longestPalindrome(s);
    cout << "The longest: " << ret << "\nLength: " << ret.size() << endl;

    return 0;
}