排序算法之冒泡排序

 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 }