各种基本算法实现小结（六）—— 查找算法

 

 

转载地址：http://blog.youkuaiyun.com/sunboy_2050/article/details/5645835

 

各种基本算法实现小结（六）—— 查找算法

（均已测试通过）

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1、简单查找

在一组无序数列中，查找特定某个数值，并返回其位置pos

测试环境：VC 6.0 (C)

[cpp:showcolumns] view plain copy print ?

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1. #include <stdio.h> 
2. #include <stdlib.h> 
3. #include <time.h> 
4. #define MAX 101 
5. void input(int num[]) 
6. { 
7.     int i; 
8.      
9.     srand((unsigned)time(NULL)); 
10.     for(i=1; i<MAX; i++) 
11.         num[i]=rand()%100; 
12. } 
13. void output(int num[]) 
14. { 
15.     int i; 
16.      
17.     for(i=1; i<MAX; i++) 
18.     { 
19.         printf("%5d", num[i]); 
20.         if(0==i%10) 
21.             printf("/n"); 
22.     } 
23. } 
24. int find(int num[], int x) 
25. { 
26.     int i; 
27.     for(i=1; i<MAX; i++) 
28.         if(x == num[i]) 
29.             return i; 
30.     return 0; 
31. } 
32. void main() 
33. { 
34.     int x, pos, num[MAX]; 
35.     input(num); 
36.      
37.     printf("num...: /n"); 
38.     output(num); 
39.      
40.     printf("Enter find num: "); 
41.     scanf("%d", &x); 
42.     pos=find(num, x); 
43.     if(pos) 
44.         printf("OK! %d is found in pos: %d/n", x, pos); 
45.     else 
46.         printf("Sorry! %d is not found... in num/n", x); 
47. } 

#include <stdio.h> #include <stdlib.h> #include <time.h> #define MAX 101 void input(int num[]) { int i; srand((unsigned)time(NULL)); for(i=1; i<MAX; i++) num[i]=rand()%100; } void output(int num[]) { int i; for(i=1; i<MAX; i++) { printf("%5d", num[i]); if(0==i%10) printf("/n"); } } int find(int num[], int x) { int i; for(i=1; i<MAX; i++) if(x == num[i]) return i; return 0; } void main() { int x, pos, num[MAX]; input(num); printf("num...: /n"); output(num); printf("Enter find num: "); scanf("%d", &x); pos=find(num, x); if(pos) printf("OK! %d is found in pos: %d/n", x, pos); else printf("Sorry! %d is not found... in num/n", x); }

运行结果：

 

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2、 折半查找

在有序数列中，逐步缩小查找范围，直至找到或找不到记录为止

本算法首先随机生成100个无序数列，然后利用快速排序算法排序成有序数列，然后再用折半查找算法

说明：本算法中的排序算法，可用上一篇排序算法中的任一种算法实现，如选择排序、冒泡排序、快速排序等

测试环境：VC 6.0 (C)

[cpp:showcolumns] view plain copy print ?

·········10········20········30········40········50········60········70········80········90········100·······110·······120·······130·······140·······150

1. #include <stdio.h> 
2. #include <stdlib.h> 
3. #include <time.h> 
4. #define MAX 101 
5. void input(int num[]) 
6. { 
7.     int i; 
8.      
9.     srand((unsigned)time(NULL)); 
10.     for(i=1; i<MAX; i++) 
11.         num[i]=rand()%100; 
12. } 
13. void output(int num[]) 
14. { 
15.     int i; 
16.      
17.     for(i=1; i<MAX; i++) 
18.     { 
19.         printf("%5d", num[i]); 
20.         if(0==i%10) 
21.             printf("/n"); 
22.     } 
23. } 
24. void sort(int num[], int low, int high) /* quick sort */ 
25. { 
26.     int l, h; 
27.      
28.     if(low<high) 
29.     { 
30.         l=low; 
31.         h=high; 
32.         num[0]=num[l]; /* save pivot */ 
33.          
34.         while(l<h) 
35.         { 
36.             while(l<h && num[h]>=num[0]) h--; 
37.                 num[l]=num[h]; 
38.             while(l<h && num[l]<=num[0]) l++; 
39.                 num[h]=num[l]; 
40.         } 
41.         num[l]=num[0]; /* insert pivot */ 
42.          
43.         sort(num, low, l-1); 
44.         sort(num, l+1, high); 
45.     } 
46. } 
47. int find(int num[], int x, int low, int high) 
48. { 
49.     int mid; 
50.      
51.     while(low<=high) 
52.     { 
53.         mid=(low+high)/2; /* find is OK */ 
54.          
55.         if(x==num[mid]) 
56.             return mid; 
57.         else if(x<num[mid]) 
58.             high=mid-1; 
59.         else 
60.             low=mid+1; 
61.     } 
62.     return 0; 
63. } 
64. void main() 
65. { 
66.     int x, pos, num[MAX]; 
67.     input(num); 
68.      
69.     printf("sort before... /n"); 
70.     output(num); 
71.     sort(num, 1, MAX-1); 
72.     printf("sort after... /n"); 
73.     output(num); 
74.      
75.     printf("Enter find num: "); 
76.     scanf("%d", &x); 
77.     pos=find(num, x, 1, MAX-1); 
78.     if(pos) 
79.         printf("OK! %d is found in pos: %d/n", x, pos); 
80.     else 
81.         printf("Sorry! %d is not found... in num/n", x); 
82. } 

#include <stdio.h> #include <stdlib.h> #include <time.h> #define MAX 101 void input(int num[]) { int i; srand((unsigned)time(NULL)); for(i=1; i<MAX; i++) num[i]=rand()%100; } void output(int num[]) { int i; for(i=1; i<MAX; i++) { printf("%5d", num[i]); if(0==i%10) printf("/n"); } } void sort(int num[], int low, int high) /* quick sort */ { int l, h; if(low<high) { l=low; h=high; num[0]=num[l]; /* save pivot */ while(l<h) { while(l<h && num[h]>=num[0]) h--; num[l]=num[h]; while(l<h && num[l]<=num[0]) l++; num[h]=num[l]; } num[l]=num[0]; /* insert pivot */ sort(num, low, l-1); sort(num, l+1, high); } } int find(int num[], int x, int low, int high) { int mid; while(low<=high) { mid=(low+high)/2; /* find is OK */ if(x==num[mid]) return mid; else if(x<num[mid]) high=mid-1; else low=mid+1; } return 0; } void main() { int x, pos, num[MAX]; input(num); printf("sort before... /n"); output(num); sort(num, 1, MAX-1); printf("sort after... /n"); output(num); printf("Enter find num: "); scanf("%d", &x); pos=find(num, x, 1, MAX-1); if(pos) printf("OK! %d is found in pos: %d/n", x, pos); else printf("Sorry! %d is not found... in num/n", x); }

运行结果：

  

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