Longest Common Prefix

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        int v_size = strs.size();
        string res = "";
        if (0 == v_size) {
            return res;
        }
        if (1 == v_size) {
            return strs[0];
        }
        int end = 1000;
        int i;
        int j;
        for (i=0; i<end; i++) {
            char tmp = strs[0][i];
            if (‘\0‘ == tmp) {
                return res;
            }
            for (j=1; j<v_size; j++) {
                if (strs[j][i] != tmp) {
                    return res;
                } 
            }
            res = res + tmp;
        }
        return res;
    }
};