LeetCode:Word Break(DP)

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

For example, given
s = "leetcode",
dict = ["leet", "code"].

Return true because "leetcode" can be segmented as "leet code".

 

分析：设状态为f(i),表示s[0,i]是否可以分词，则状态转移方程为

　　f(i)=any_of(f(j)&&s[j+1,i]属于wordDict); 0<=j<i

class Solution {
public:
    bool wordBreak(string s, unordered_set<string>& wordDict) {
        vector<bool> f(s.size()+1,false);
        f[0]=true;
        
        for(int i=1;i<=s.size();++i)
            for(int j=i-1;j>=0;--j)
                if(f[j]&&wordDict.find(s.substr(j,i-j))!=wordDict.end())
                {
                    f[i]=true;
                    break;
                }
        return f[s.size()];
        
    }
};