14. Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

S: vertical enumeration O(mn)

    string longestCommonPrefix(vector<string>& strs) {
        string prefix = "";
        if(strs.empty()) return prefix;
        for(int i = 0; i < strs[0].size(); ++i){
            for(int j = 1; j < strs.size(); ++j){
                if(i >= strs[j].size() || strs[j][i] != strs[0][i]) return prefix;
            }
            prefix += strs[0][i];
        }
        return prefix;
    }