#14 Longest Common Prefix

思路很简单 循环比对每个数字的前i个字符 直到不相同

  /**
  * @param {string[]} strs
  * @return {string}
  */
  var longestCommonPrefix = function(strs) {
    var j = strs.length,k = 0,res = "";
    if(j === 0)
      return "";
    if(j === 1)
      return strs[0];

    while(check(k)) {
      res += strs[0][k++];
    }

    return res;

    function check(pos) {
      var i = 0;
      for(;i < j - 1; i++) {
        if(strs[i][pos] !== strs[i + 1][pos] || strs[i][pos] === undefined)
          return false
      }
      return true;
    }
  };