LeetCode:Word Break（DP）

题目地址：http://oj.leetcode.com/problems/word-break/

简单的动态规划问题，采用自顶向下的备忘录方法，代码如下：

 class Solution {
 public:
     bool dictContain(unordered_set<string> &dict, string s)
     {
         unordered_set<string>::iterator ite = dict.find(s);
         if(ite != dict.end())
             return true;
         else return false;
     }

     bool wordBreak(string s, unordered_set<string> &dict)
     {
         // Note: The Solution object is instantiated only once and is reused by each test case.
         if(dict.empty())
             return false;
         const int len = s.size();
         bool canBreak[len]; //canBreak[i] = true 表示s[0~i]是否能break
         memset(canBreak, , sizeof(bool)*len);
         for(int i = ; i <= len; i++)
         {
             if(canBreak[i-] == false && dictContain(dict, s.substr(, i)))
                 canBreak[i-] = true;

             if(canBreak[i-] == true)
             {
                 if(i == len)return true;
                 for(int j = ; j <= len - i; j++)
                 {
                     if(canBreak[j+i-] == false && dictContain(dict,s.substr(i, j)))
                         canBreak[j+i-] = true;

                     if(j == len - i && canBreak[j+i-] == true)return true;

                 }
             }

         }

         return false;
     }

 };

注意：在本机调试时，编译器要开启c++11支持，因为#include<unordered_set>是c++11的标准

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