LeetCode OJ——Word Break

http://oj.leetcode.com/problems/word-break/

动态规划题目，重点是建立出模型来：

fun(start,end) = fun(start,i)*fun(i+1,end);

二维动态数组的申请：

int len = s.length();
int **flag = new int *[len];
for(int i = 0;i<len;i++)
    flag[i] = new int [len];

#include <iostream>
#include <string>
#include <unordered_set>
using namespace std;

class Solution {
public:
    bool fun(string s,unordered_set<string> &dict,int start,int end,int **flag)
    {
        if(flag[start][end]==1)
            return true;
        if(flag[start][end]==-1)
            return false;
        string subString = s.substr(start,end-start+1);
        if(dict.find(subString)!=dict.end())
            return true;
        for(int i = start;i<end;i++)
            if(fun(s,dict,start,i,flag)*fun(s,dict,i+1,end,flag))
            {
                flag[start][end] = 1;
                return 1;
            }
        flag[start][end] = -1;
        return false;
    }
    bool wordBreak(string s, unordered_set<string> &dict) {
        int len = s.length();
        int **flag = new int *[len];
        for(int i = 0;i<len;i++)
            flag[i] = new int [len];
         
        return fun(s,dict,0,len-1,flag);
    }
};

int main()
{
    class Solution mys;
    string s = "leetcode";
    unordered_set<string> dict;
    dict.insert("le");
    //dict.insert("et");
    dict.insert("code");
    cout<<mys.wordBreak(s,dict);
    return 0;
}