各种排序算法
基础才是最重要的， 好久不写排序了，今天写了一下还是各种报错。。。。
要养成习惯，每天至少做一道算法题
1 //复习各种排序 2 public class SortApp { 3 4 public static void main(String[] args) { 5 int[] a = {5,23,7,18,56,2,36,5,3,9,6,4,1}; 6 SortApp app = new SortApp(); 7 //app.quickSort(a); 8 //app.selectSort(a); 9 //app.insertSort(a); 10 app.bubbleSort(a); 11 app.display(a); 12 } 13 14 //快速 15 void quickSort(int[] a){ 16 quickSort(a, 0, a.length - 1); 17 } 18 19 private void quickSort(int[] a, int left, int right){ 20 if(left >= right) return; 21 int pivot = left; 22 int i = left, j = right + 1; 23 24 while(i<j){ 25 while(a[++i] < a[pivot] && i < right); 26 while(a[--j] > a[pivot] && j > 0); 27 if(i<j)swap(a, i, j); 28 } 29 swap(a,pivot, j); 30 31 quickSort(a, left, j-1); 32 quickSort(a, j+1, right); 33 } 34 35 //冒泡 36 void bubbleSort(int[] a){ 37 for(int i = 0; i < a.length; i++){ 38 for(int j = 1; j < a.length - i; j++){ 39 if(a[j-1] >= a[j]){ 40 swap(a,j-1,j); 41 } 42 } 43 } 44 } 45 46 //插入 47 void insertSort(int[] a){ 48 for(int i = 1; i < a.length; i++){ 49 int current = a[i]; 50 //pointer for the previous element of i 51 int j = i-1; 52 while(j>=0 && a[j] > current){ 53 a[j+1] = a[j]; 54 j--; 55 } 56 57 //now j points to the element which is smaller than a[i] 58 a[j+1] = current; 59 } 60 } 61 62 //选择 63 void selectSort(int[] a){ 64 for(int i = 0; i < a.length; i++){ 65 int min = i; 66 for(int j = i+1; j < a.length; j++){ 67 if(a[j] < a[min]) min = j; 68 } 69 swap(a, i, min); 70 } 71 } 72 73 private void swap(int[] a, int i, int j){ 74 int tmp = a[i]; 75 a[i] = a[j]; 76 a[j] = tmp; 77 } 78 79 private void display(int[] a){ 80 for(int i: a){ 81 System.out.print(" " + i); 82 } 83 System.out.println(""); 84 } 85 }
