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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. int binary_search(int a[],int n,int x){
  5. 	int left = 0;
  6. 	int right = n - 1;
  7. 	int center;
  8.  
  9. 	while(left <= right){
  10. 		center = (left + right) / 2;
  11.  
  12. 		if(a[center] == x){
  13. 			return center;
  14. 		}
  15. 		else if(a[center] < x){
  16. 			left = center + 1;
  17. 		}
  18. 		else{
  19. 			right = center - 1;
  20. 		}
  21. 	}
  22.  
  23. 	return -1;
  24. }
  25.  
  26. int main(void) {
  27. 	int n,x,i;
  28. 	int *a;
  29. 	int ans = -1;
  30.  
  31. 	scanf("%d %d",&n,&x);
  32.  
  33. 	a = (int*)malloc(sizeof(int)*n);
  34.  
  35. 	if(a==NULL){
  36. 		printf("ERROR\n");
  37. 		return -1;
  38. 	}
  39.  
  40. 	for(i=0;i<n;i++){
  41. 		scanf("%d",&a[i]);
  42. 	}
  43.  
  44. 	ans = binary_search(a,n,x);
  45.  
  46. 	if(ans != -1){
  47. 		printf("a[%d] = %d\n",ans,a[ans]);
  48. 	}
  49. 	else{
  50. 		printf("not found\n");
  51. 	}
  52.  
  53. 	free(a);
  54.  
  55. 	return 0;
  56. }
Success #stdin #stdout 0s 5288KB
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/meSMkm
language:
C (gcc 8.3)
created:
21 hours ago
visibility:
public

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