codewars--js--Range Extraction

问题描述：

A format for expressing an ordered list of integers is to use a comma separated list of either

• individual integers
• or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. The range includes all integers in the interval including both endpoints. It is not considered a range unless it spans at least 3 numbers. For example ("12, 13, 15-17")

Complete the solution so that it takes a list of integers in increasing order and returns a correctly formatted string in the range format.

Example:

solution([-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20]);
// returns "-6,-3-1,3-5,7-11,14,15,17-20"

解题思路：

我一般写代码的顺序就是按照自己手工做题的顺序。当连续的数字小于3时，分别输入；当连续的数字超过3时，例如“-3，-2，-1， 0, 1”记做“-3-1”。

该题有两个判断（连续数字数量是否超过3，数字是否连续）

我的答案：

function solution(list){
 // TODO: complete solution 
 var flag=0;
 var b=[];
 for (let i=0;i<list.length;i++){
   if(list[i]+1!=list[i+1]){
     if(flag==0){b.push(list[i]);}
     if(flag==1){b.push(list[i-1]);b.push(list[i]);flag=0;}
     if(flag>1){b.push(list[i-flag]+"-"+list[i]);flag=0;}
   }else{
     flag++;
   }
 }
 return b.join();
}

优秀答案：

（1）

function solution(list){
   for(var i = 0; i < list.length; i++){
      var j = i;
      while(list[j] - list[j+1] == -1) j++;
      if(j != i && j-i>1) list.splice(i, j-i+1, list[i] +'-'+list[j]); //从list[i]开始的连续（j-i+1）个数字换成

                                                                       //list[i] +'-'+list[j]

} return list.join(); }

（2）

function solution(list){
 // TODO: complete solution 
  var res = list.slice();

  for(var i = 0; i < list.length; ++i) {
      if(i === 0 || i === list.length - 1) continue;  //忽略首尾数字
      if(res[i] - 1 === list[i - 1] && res[i] + 1 === list[i + 1]) { //将满足左边比它小1，右边大1 的数字变成null
        res[i] = null;
      }
  }

  return res.toString().replace(/,{2,}/g, '-');  //将连续的至少2个的，换成-

哈哈哈。