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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. //この関数を実装する
  5. int binary_search(int a[],int n,int x){
  6. 	int ret=-1;
  7. 	int lef, mid, rig;
  8. 	lef=0;
  9. 	rig=n-1;
  10. 	while(lef<=rig){
  11. 		mid=(lef+rig)/2;
  12. 		if(a[mid]==x){
  13. 		ret=mid;
  14. 		break ;
  15. 	}
  16. 	if(a[mid]<x)
  17. 		lef=mid+1;
  18. 	else
  19. 	rig=mid-1;
  20. 	}
  21. 	return ret;
  22. }
  23.  
  24. int main(void) {
  25. 	int n,x,i;
  26. 	int *a;
  27. 	int ans = -1;
  28. 	scanf("%d %d",&n,&x);
  29. 	a = (int*)malloc(sizeof(int)*n);
  30. 	if(a==NULL){
  31. 		printf("ERROR\n");
  32. 		return -1;
  33. 	}
  34. 	for(i=0;i<n;i++){
  35. 		scanf("%d",&a[i]);
  36. 	}
  37. 	ans = binary_search(a,n,x);
  38. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  39. 	else printf("not found\n");
  40. 	free(a);
  41. 	return 0;
  42. }
Success #stdin #stdout 0s 5312KB
comments (?)
stdin
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5 7
1 4 7 8 12
stdout
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a[2] = 7
https://ideone.com/ecur3V
language:
C (gcc 8.3)
created:
2 days ago
visibility:
public

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