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  1. //第3回 課題１
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4.  
  5. //この関数を実装する
  6. int binary_search(int a[],int n,int x){
  7. 	//この関数の内側だけを書く
  8. 	int lef=0, mid, rig=n-1;
  9. 	mid=(lef+rig)/2;
  10. 	while(1){
  11. 	if(a[mid]==x)
  12. 	break;
  13. 	else if(x < a[mid]){
  14. 		rig=mid-1;
  15. 		mid=(lef+rig)/2;	
  16. 	}
  17. 	else if(a[mid] < x){
  18. 		lef=mid+1;
  19. 		mid=(lef+rig)/2;
  20. 	}
  21. 	else 
  22. 	x=-1;
  23. 	}
  24. 	return mid;
  25. }
  26.  
  27. int main(void) {
  28. 	int n,x,i;
  29. 	int *a;
  30. 	int ans = -1;
  31. 	scanf("%d %d",&n,&x);
  32. 	a = (int*)malloc(sizeof(int)*n);
  33. 	if(a==NULL){
  34. 		printf("ERROR\n");
  35. 		return -1;
  36. 	}
  37. 	for(i=0;i<n;i++){
  38. 		scanf("%d",&a[i]);
  39. 	}
  40. 	ans = binary_search(a,n,x);
  41. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  42. 	else printf("not found\n");
  43. 	free(a);
  44. 	return 0;
  45. }
  46.  
Success #stdin #stdout 0s 5320KB
comments (?)
stdin
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12 5
1 2 3 4 5 8 9 13 16 21 25 27
stdout
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a[4] = 5
https://ideone.com/eyKXB5
language:
C99 (gcc 8.3)
created:
3 days ago
visibility:
public

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