Word Break问题及解法

问题描述：

Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words. You may assume the dictionary does not contain duplicate words.

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

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

问题分析：

这是一道可用动态规划求解的问题，对于数组s若能分割为dict中的若干个单词，那么肯定存在s的字串s1和s2满足s在dict中所满足的条件。

过程详见代码：

class Solution {public:    bool wordBreak(string s, vector<string>& wordDict) {        unordered_set<string> dict(wordDict.begin(), wordDict.end());int n = s.length();vector<bool> dp(n, 0);dp[0] = (dict.find(s.substr(0, 1)) != dict.end());for (int i = 1; i < n; i++){dp[i] = (dict.find(s.substr(0, i + 1)) != dict.end());for (int j = i - 1; j >= 0; j--){if (dp[i]) break;if (!dp[j]) continue;dp[i] = (dict.find(s.substr(j + 1, i - j)) != dict.end());}}return dp[n-1];    }};