排序算法之冒泡排序

 

题目传送门

 1 /*  2  BubbleSort_2(),_3()为优化版  3  用zstu3539题目来验证算法的正确性  4 */  5 #include <cstdio>  6 #include <iostream>  7 #include <algorithm>  8 #include <ctime>  9 #include <cstdlib> 10 using namespace std; 11 12 const int maxn = 1000000 + 10; 13 const int INF = 0x3f3f3f3f; 14 int a[maxn]; 15 16 void BubbleSort(int *a, int n) 17 { 18 for (int i=1; i<=n-1; ++i) 19  { 20 for (int j=1; j<=n-i; ++j) 21  { 22 if (a[j] > a[j+1]) swap (a[j], a[j+1]); 23  } 24  } 25 } 26 27 void BubbleSort_2(int *a, int n) //若不进行交换，已排好序，算法结束 28 { 29 30 for (int i=1; i<=n-1; ++i) 31  { 32 int pos = 0; 33 for (int j=1; j<=n-i; ++j) 34  { 35 if (a[j] > a[j+1]) 36  { 37 swap (a[j], a[j+1]); 38 pos = j; 39  } 40  } 41 if (pos == 0) break; 42  } 43 } 44 45 void BubbleSort_3(int *a, int n) //一次冒泡得到最大值和最小值，排序次数几乎减少一半 46 { 47 int l = 1, r = n; 48 while (l < r) 49  { 50 for (int i=l; i<r; ++i) //正向冒泡 51  { 52 if (a[i] > a[i+1]) swap (a[i], a[i+1]); 53  } 54 --r; 55 for (int i=r; i>l; --i) //反向冒泡 56  { 57 if (a[i] < a[i-1]) swap (a[i], a[i-1]); 58  } 59 ++l; 60  } 61 } 62 63 int main(void) 64 { 65 //freopen ("rand_small.in", "r", stdin); 66 int n; 67 68 while (scanf ("%d", &n) != EOF) 69  { 70 if (n == 0) 71 continue; 72 for (int i=1; i<=n; ++i) 73  { 74 scanf ("%d", &a[i]); 75  } 76 77  BubbleSort (a, n); 78 //BubbleSort_2 (a, n); 79 //BubbleSort_3 (a, n); 80 81 bool flag = true; 82 for (int i=1; i<=n; ++i) 83  { 84 if (flag) 85  { 86 printf ("%d", a[i]); 87 flag = false; 88  } 89 else 90 printf (" %d", a[i]); 91  } 92 puts (""); 93  } 94 95 return 0; 96 }