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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 lef = 0;
  8.     int rig = n-1;
  9. 	while (lef <= rig) 
  10. 	{
  11. 		int mid = (lef + rig)/2;
  12. 		if (a[mid] == x)
  13. 		{   
  14. 			return mid;
  15. 		}
  16. 		else if (a[mid] < x)
  17. 		{
  18.             lef = mid + 1;
  19.         }
  20. 		else
  21. 		{
  22.             rig = mid - 1;
  23.         }
  24. 	}
  25.  return -1;
  26. }
  27.  
  28. int main(void) {
  29. 	int n,x,i;
  30. 	int *a;
  31. 	int ans = -1;
  32. 	scanf("%d %d",&n,&x);
  33. 	a = (int*)malloc(sizeof(int)*n);
  34. 	if(a==NULL){
  35. 		printf("ERROR\n");
  36. 		return -1;
  37. 	}
  38. 	for(i=0;i<n;i++){
  39. 		scanf("%d",&a[i]);
  40. 	}
  41. 	ans = binary_search(a,n,x);
  42. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  43. 	else printf("not found\n");
  44. 	free(a);
  45. 	return 0;
  46. }
  47.  
Success #stdin #stdout 0s 5276KB
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/Oi0WXH
language:
C (gcc 8.3)
created:
236 days ago
visibility:
public

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