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".

----------------------------

动态规划，F(n) = (F(i) && s.substr( i, n - i))  --- i in range [0, n].

class Solution {
public:
    bool wordBreak(string s, unordered_set<string> &dict) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int slen = s.length();
        bool ret[slen + 1];
        fill(ret, ret + slen + 1, false);
        ret[0] = true;
        for (int i = 1; i <= slen; i++) {
            for (int j = i; j > 0; j--) {
                if (ret[j - 1] && dict.count(s.substr(j - 1, i - j + 1)) > 0) {
                    ret[i] = true;
                    break;
                }
            }
        }
        
        return ret[slen];
    }
};