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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 lef=0;
  7. 	int rig=n-1;
  8.  
  9. 	while(lef<=rig){
  10. 		int mid=(lef+rig)/2;
  11. 		if(a[mid]==x){
  12. 			return mid;
  13. 		}
  14. 		else if(a[mid]<x){
  15. 			lef=mid+1;
  16. 		}else{
  17. 			rig=mid-1;
  18. 		}
  19. 	}
  20. 	return -1;
  21. }
  22.  
  23. int main(void) {
  24. 	int n,x,i;
  25. 	int *a;
  26. 	int ans = -1;
  27. 	scanf("%d %d",&n,&x);
  28. 	a = (int*)malloc(sizeof(int)*n);
  29. 	if(a==NULL){
  30. 		printf("ERROR\n");
  31. 		return -1;
  32. 	}
  33. 	for(i=0;i<n;i++){
  34. 		scanf("%d",&a[i]);
  35. 	}
  36. 	ans = binary_search(a,n,x);
  37. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  38. 	else printf("not found\n");
  39. 	free(a);
  40. 	return 0;
  41. }
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
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10 5
1 2 3 4 5 6 7 8 9 10
stdout
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a[4] = 5
https://ideone.com/mSnWAl
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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