[LintCode] Longest Common Prefix

Given k strings, find the longest common prefix (LCP).

Example

For strings "ABCD", "ABEF" and "ACEF", the LCP is "A"

For strings "ABCDEFG", "ABCEFG" and "ABCEFA", the LCP is"ABC"

class Solution {
public:    
    string longestCommonPrefix(vector<string> &strs) {
        int len = strs.size();
        string res;
        if(0 == len) return res;
        int index = 0;
        
        while(index<strs[0].length())
        {
            for(int i=1;i<len;i++)
            {
                if(strs[i][index] != strs[0][index]) 
                {
                    return strs[0].substr(0, index);
                }
            }
            index++;
        }
        return strs[0];
    }
};