1 #include"header_file.h"
2 using namespace std;
3
4 void swap(int a,int b)
5 {
6 int t;
7 t=a;
8 a=b;
9 b=t;
10 }
11
12 void quick_sort(int a[],int low,int high)
13 {
14
15 if(low>=high)
16 return;
17
18 int first;
19 int last;
20 first=low;
21 last=high;
22
23 int x;
24 x=a[low];
25
26
27 while(low<high)
28 {
29 while(low<high&&a[high]>=x)
30 {
31 high--;
32 }
33 swap(a[low],a[high]);
34
35 cout<<i<<" "<<low<<" low"<<" "<<high<<endl;
36
37 while(low<high&&a[low]<=x)
38 {
39 low++;
40 }
41 swap(a[high],a[low]);
42 cout<<i<<" "<<low<<" high"<<" "<<high<<endl;
43 }
44 if(first<low-1)
45 quick_sort(a,first,low-1);
46 if(last>low+1)
47 quick_sort(a,low+1,last);
48 }
49
50 int main(void)
51 {
52 int a[7]={4,3,6,7,2,1,5};
53 quick_sort(a,0, sizeof(a) / sizeof(a[0]) - 1);
54
55 cout<<"test"<<endl;
56 for(int i=0;i<7;i++)
57 cout<<a[i]<<" ";
58 }
執行程序會發現在算法排序的地方無限循環，想了半天才知道是33和41行的位置，不管while循環是否執行都會執行swap語句。邏輯錯誤！
只能換種方法，改成大家最常見的那種就好了
1 void quick_sort(int a[],int low,int high)
2 {
3
4 if(low>=high)
5 return;
6
7 int first;
8 int last;
9 first=low;
10 last=high;
11
12 int x;
13 x=a[low];
14
15
16 while(low<high)
17 {
18 while(low<high&&a[high]>=x)
19 {
20 high--;
21 }
22 a[low]=a[high];
23
24 // cout<<i<<" "<<low<<" low"<<" "<<high<<endl;
25
26 while(low<high&&a[low]<=x)
27 {
28 low++;
29 }
30 a[high]=a[low];
31 // swap(a[high],a[low]);
32 // cout<<i<<" "<<low<<" high"<<" "<<high<<endl;
33 }
34 a[low]=x;
35
36 if(first<low-1)
37 quick_sort(a,first,low-1);
38 if(last>low+1)
39 quick_sort(a,low+1,last);
40 }
這裡就不是交換了，直接賦值，然後最後給a[low]賦值。
很低級的錯誤
