leetcode longestCommonPrefix - https://leetcode.com/problems/longest-common-prefix

longestCommonPrefix.js

/*
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: strs = ["flower","flow","flight"]
Output: "fl"

Example 2:

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

Constraints:

    1 <= strs.length <= 200
    0 <= strs[i].length <= 200
    strs[i] consists of only lowercase English letters.
*/

var longestCommonPrefix = function(strs) {
    // sort by abc
    strs = strs.sort(function(a, b) { return (a > b ? 1 : (a === b ? 0 : -1)) })

    const allEqual = arr => arr.every(val => val === arr[0])
    var isAllEqual = allEqual(strs)
    if (isAllEqual) {
        return strs[0]
    }

    if (strs.length === 1) {
        return strs[0]
    }

    var shortestWord = strs.reduce(function(a, b) { return a.length <= b.length ? a : b })
    var shortestWordLen = shortestWord.length
    var shortestWordFirstLetter = shortestWord[0]
    
    if (shortestWordLen === 1) {
        shortestWordLen += 1
    }

    if (strs.length === 2) {
        if (strs[0] == "" && strs[1] == "") {
            return ""
        }

        if (!strs[1].startsWith(strs[0][0])) {
            return ""
        }
    }
    
    var solution = ""

    for (var i = 0; i <= shortestWordLen; i++) { 
        if (i === 0) {
            key = strs[0].slice(0, 1)
        } 
        else {
            key = strs[0].slice(0, i)
        }

        for (var j = 0; j < strs.length; j++) {
            if (strs[j].startsWith(key)) {
                continue
            }

            if (!strs[j].startsWith(key)) {
                return solution
            }
        }
        solution = key
    }
    return solution
}