Word Break

Description:

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

Example

Given s = "lintcode", dict = ["lint", "code"].

Return true because "lintcode" can be break as "lint code".

Solution:

class Solution {
public:
	/**
	 * @param s: A string s
	 * @param dict: A dictionary of words dict
	 */
	bool wordBreak(string s, unordered_set<string> &dict) {
		// write your code here
		auto len = (int)s.length();
		if (len == 0) return true;
		vector<bool> vec(len+1, false);
		vec[0] = true;
		int maxLen = 0;
		for (auto& e : dict) maxLen = max(maxLen, (int)e.length());
		for (int i = 1; i <= len; ++i) {
			for (int j = i-1; j >= 0 && i-j <= maxLen; --j) {
				if (!vec[j]) continue;
				if (dict.find(s.substr(j, i-j)) != dict.end()) {
					vec[i] = true;
					break;
				}
			}
		}
		return vec[len];
	}
};