[LeetCode] Longest Common Prefix

Use the strs[0] as the reference string and then compare it with the remaining strings from left to right. Once we find a string with length less than strs[0] or different letters in the corresponding position, we cannot move on and should return the longest common prefix string lcp. Each time we finish checking a position and have not returned, we add the letter at that position to lcp.

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if (strs.empty()) return "";
        string lcp = "";
        int m = strs.size(), n = strs[0].length();
        for (int i = 0; i < n; i++) {
            for (int j = 1; j < m; j++)
                if (strs[j].length() == i || strs[j][i] != strs[0][i])
                    return lcp;
            lcp += strs[0][i];
        }
        return lcp;
    }
};