14. Longest Common Prefix

描述

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.

解决方案

思路：从第二个字符串开始，都与第一个字符串比较相同位置的字符，如果相同，则指针向后移一位，否则，返回第一个字符串从0开始，到n-1截取即是最长公共前缀。

public String longestCommonPrefix(String[]strs){
    if(strs==null||strs.length==0)return "";
    int preCount=0;
    boolean exit = false;
    while(true){
        if(strs[0].length()==preCount){
            break;
        }
        char a=strs[0].charAt(preCount);
        for(int i=1;i<strs.length;i++)
            if(strs[i].length()==preCount||a!=strs[i].charAt(preCount)){
                exit = true;
            }
        }
        if(exit){
            break;
        }
        preCount++;
    }
    return strs[0].substring(0,preCount);
}