LeetCode 14. Longest Common Prefix (javascript)

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:

• 0 <= strs.length <= 200
• 0 <= strs[i].length <= 200
• strs[i] consists of only lower-case English letters.

Idea:

• Use first string for comparison
• loop through each string:
  • store the common letter if match
  • or return the answer if no match

Solution:

/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function(strs) {
    if (strs === null || strs.length === 0) return "";
    let ans = "";
    for (let i = 0; i < strs[0].length; i++) {
        for (let s of strs) {
            if (s.length <= i || s[i] !== strs[0][i]) return ans;
        }   
        ans += strs[0][i];
    }
        
    return ans;
};