중복되는 가장 긴 접두사를 출력하는 함수
Input: strs = ["flower","flow","flight"]
Output: "fl"
var longestCommonPrefix = function(strs) {
let result = '';
if(strs.length === 1) return strs[0];
for(let x = 0; x < strs[0].length; x++){
for(let y = 1; y < strs.length; y++){
if(strs[0][x] !== strs[y][x]){
return result;
}
}
result += strs[0][x];
}
return result;
};