js 算法

一、排序

1. 插入算法

   let arr = [7, 4, 1, 2, 6, 8, 3, 5, 9]
   
   function insertSort (arr) {
       for (let i = 0; i < arr.length; i++) {
           let temp = arr[i];
           let j = i - 1;
           
           while(j >= 0 && arr[j] > temp) {
               arr[j + 1] = arr[j]
               j--;
           }
           arr[j + 1] = temp;
       }
       return arr;
   }
   
   console.log(insertSort(arr))

2. 冒泡算法

   let arr = [7, 4, 1, 2, 6, 8, 3, 5, 9]
   
   function bubbleSort (arr) {
       for (let i=0; i < arr.length; i++) {
           for (let j=0; j < arr.length; j++) {
               if(arr[j] > arr[j+1]) {
                   [arr[j], arr[j+1]] = [arr[j+1], arr[j]];
               }
           }
       }
       return arr;
   }
   
   console.log(bubbleSort(arr))

3. 选择排序

   let arr = [7, 4, 1, 2, 6, 8, 3, 5, 9]
   
   function selectSort (arr) {
       for (let i=0; i<arr.length; i++) {
           let temp;
           for (let j = i + 1; j < arr.length; j++) {
               if (arr[i] > arr[j]) {
                   [arr[i], arr[j]] = [arr[j], arr[i]]
               }
           }
       }
       return arr;
   }
   
   console.log(selectSort(arr));

4. 希尔排序

   let arr = [7, 4, 1, 2, 6, 8, 3, 5, 9]
   
   function shellSort(arr) {
       let n = arr.length;
       let gap = Math.floor(n/2);
   
       while(gap >= 1) {
           for(let i=gap; i < arr.length; i++) {
               let temp = arr[i];
               let j = i;
               while(j >= gap && arr[j-gap] > temp) {
                   arr[j] = arr[j-gap]
                   j = j-gap;
               }
               arr[j] = temp;
           }
           gap = Math.floor(gap/2);
       }
       return arr;
   }
   
   console.log(shellSort(arr));