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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. 	int ret = -1;
  8. 	int lef,mid,rig;
  9. 	lef = 0;
  10. 	rig = n-1;
  11. 	while(lef <= rig){
  12. 		mid = (lef + rig)/2;
  13. 		//printf("%d %d %d:%d\n",lef,mid,rig,a[mid]);
  14. 		if(a[mid] == x){
  15. 			ret = mid;
  16. 			break;
  17. 		}
  18. 		if(x < a[mid])
  19. 		rig = mid-1;
  20. 		else
  21. 		lef = mid+1;
  22. 	}
  23. 	return ret;
  24. }
  25.  
  26. int main(void) {
  27. 	int n,x,i;
  28. 	int *a;
  29. 	int ans = -1;
  30. 	scanf("%d %d",&n,&x);
  31. 	a = (int*)malloc(sizeof(int)*n);
  32. 	if(a==NULL){
  33. 		printf("ERROR\n");
  34. 		return -1;
  35. 	}
  36. 	for(i=0;i<n;i++){
  37. 		scanf("%d",&a[i]);
  38. 	}
  39. 	ans = binary_search(a,n,x);
  40. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  41. 	else printf("not found\n");
  42. 	free(a);
  43. 	return 0;
  44. }
  45.  
Success #stdin #stdout 0s 5288KB
comments (?)
stdin
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5 7
1 3 5 7 9
stdout
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a[3] = 7
https://ideone.com/kyc63g
language:
C (gcc 8.3)
created:
9 days ago
visibility:
public

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