Word Break

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".

 

Runtime: 6ms

class Solution {
public:
    bool wordBreak(string s, unordered_set<string>& wordDict) {
        if (s.empty()) return true;
        
        // Have dp[i] indicate whether s[0...i-1] could be broken.
        // If there is a dp[j] where j from [0, i - 1] is true, 
        // and s[j...i - 1] is in the dictionary, then dp[i] is true
        vector<bool> dp(s.size() + 1, false);
        dp[0] = true;
        for (int i = 1; i <= s.size(); i++) {
            for (int j = i; j >= 0; j--) {
                if (dp[j] && wordDict.count(s.substr(j, i - j)) > 0) {
                    dp[i] = true;
                    break;
                }
            }
        }
        return dp[s.size()];
    }
};