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;
}