Longest common prefix and

Write a function to find the longest common prefix in the string array .

If no common prefix exists , Returns an empty string “”.

Example 1：

Input ：strs = [“flower”,“flow”,“flight”]
Output ：“fl”
Example 2：

Input ：strs = [“dog”,“racecar”,“car”]
Output ：""
explain ： Input does not have a common prefix .

//  First assume the longest public prefix ans Is the first , Traverse each subsequent string , And ans Go through one by one , Record subscript if different , Intercept ans return 
var longestCommonPrefix = function (strs) {
    
    if (!strs.length) return ''
    let ans = strs[0]
    //  Traversal string array 
    for (let i = 1; i < strs.length; i++) {
    
        //  Traversing every character of a string 
        let tmp
        if (!strs[i].length) return ''
        for (let j = 0; j < strs[i].length; j++) {
    
            //  and ans contrast , Different ends convenience , here j It's the next one in a different position index
            if (ans[j] != strs[i][j]) {
    
                tmp = j
                break
            }
            tmp = j + 1
        }
        ans = ans.substr(0, tmp)
    }
    return ans
};

longestCommonPrefix(["abab", "aba", ""])