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.

/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function(strs) {
    var str = strs.sort();
    //对数组进行排序,对第一个和最后一个进行比较
    var last = str[str.length-1];
    var first = str[0];
    if(!first){
       return "";
    }
    var newStr="";
    for(var i = 0; i < first.length; i++){
        if(first[i] === last[i]){
            newStr = newStr + first[i];
        }else{
            break;
        }
    }
    return newStr;
};