14 . Longest Common Prefix

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

If there is no common prefix, return an empty string "".

Example 1:

Input: ["flower","flow","flight"]
Output: "fl"
Example 2:

Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.
Note:

All given inputs are in lowercase letters a-z.

IndexOf : find the index of the substring

Edwardshi Edward Ed 
Ans = Edwardshi

(Edward).indexOf(ans) != 0
    Ans = Edwardsh
(Edward).indexOf(ans) != 0
    Ans = Edwards
(Edward).indexOf(ans) != 0
    Ans = Edward
(Ed).indexOf(ans) != 0
   Ans = Edwar
(Ed).indexOf(ans) != 0
   Ans = Edwa
(Ed).indexOf(ans) != 0
   Ans = Edw
(Ed).indexOf(ans) != 0
   Ans = Ed

从

class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null || strs.length == 0) {
            return "";
        }
        String ans = strs[0];
        for (int i = 1; i < strs.length; i++) {
            while (strs[i].indexOf(ans) != 0) {
                ans = ans.substring(0, ans.length() - 1);
            }
        }
        return ans;
    }
}