[LeetCode]139.单词拆分（C++）

1.代码

class Solution {
public:bool wordBreak(string s, vector<string>& wordDict) {int length = s.size();bool *count1 = new bool[length+1];fill(count1, count1 + length + 1, false);unordered_map<string, bool> hashTable;count1[0] = true;for(int i = 0;i < wordDict.size();i ++){hashTable[wordDict[i]] = true;}for(int i = 1;i <= length;i ++){for(int j = 0;j < i;j ++){if(count1[j] && hashTable.count(s.substr(j,i-j))>0){count1[i] = true;break;}}}return count1[length];}
};

2.思路

用了动态规划，用一个count1数组记录字符串的前i个字母是否能拆分成单词，状态转移方程是count1[i] = count1[j] &&hashTable.count(s.substr(j,i-j))>0。