[14] 最长公共前缀

// @lc code=start
/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function (strs) {
  var ll = strs.length;
  if (ll === 0) {
    return "";
  } else if (ll === 1) {
    return strs[0];
  } else {
    var ans = strs[0];
    for (var i = 0; i < ll; i++) {
      var ansl = ans.length;
      var s = strs[i];
      var sl = s.length;
      if (sl < ansl) {
        ansl = sl;
      }
      var j = ansl;
      for (; j > 0;) {
        ans = ans.substring(0, j);
        s = s.substring(0, j);
        if (ans !== s) {
          j--;
        } else {
          break;
        }
      }
      if (j === 0) {
        return "";
      }
    }
  }
  return ans;
};