算法竞赛入门经典习题2-6 排列(permutation)

暴力解法:

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3
 4 int compare(const void *a, const void *b);
 5
 6 int main(int argc, char **argv){
 7     int i,j,k;
 8     int arr[9];
 9     for(i=100;i<333;i++){
10     for(j=200;j<666;j++){
11         for(k=300;k<1000;k++){
12         arr[0] = i/100;
13         arr[1] = (i/10)%10;
14         arr[2] = i%10;
15         arr[3] = j/100;
16         arr[4] = (j/10)%10;
17         arr[5] = j%10;
18         arr[6] = k/100;
19         arr[7] = (k/10)%10;
20         arr[8] = k%10;
21         qsort(arr, 9, sizeof(int),compare);
22         int m;
23         for( m = 0; m<9; m++){
24             if(arr[m] != m+1){
25             break;
26             }
27         }
28         if(m == 9){
29             if(k%i==0 && j%i == 0 && k/i == 3 && j/i == 2){
30             printf("%d %d %d\n",i,j,k);
31             }
32         }
33         }
34     }
35     }
36     return 0;
37 }
38 int compare(const void *a, const void *b){
39     return *(int*)a - *(int*)b;
40 }

vs.

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3
 4 int compare(const void *a, const void *b);
 5
 6 int main(int argc, char **argv){
 7     int arr[9];
 8     int abc, def, ghi;
 9     for(abc = 100; abc <334; abc++){
10     def = 2 * abc;
11     ghi = 3 * abc;
12     arr[0] = abc/100;
13     arr[1] = (abc/10)%10;
14     arr[2] = abc%10;
15     arr[3] = def/100;
16     arr[4] = (def/10)%10;
17     arr[5] = def%10;
18     arr[6] = ghi/100;
19     arr[7] = (ghi/10)%10;
20     arr[8] = ghi%10;
21     qsort(arr, 9, sizeof(int), compare);
22     int m;
23     for( m = 0; m<9; m++){
24         if(arr[m] != m+1){
25         break;
26         }
27     }
28     if(m == 9){
29         printf("%d %d %d\n",abc, def, ghi);
30     }
31     }
32     return 0;
33 }
34
35 int compare(const void *a, const void *b){
36     return *(int*)a - *(int*)b;
37 }