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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 l=0;
  8. 	int r=n-1;
  9. 	int m;
  10.  
  11. 	while(l<=r){
  12. 		m=(l+r)/2;
  13.  
  14. 		if(a[m]==x){
  15. 			return m;
  16. 		}
  17. 		else if(a[m]<x){
  18. 			l=m+1;
  19. 		}
  20. 		else{
  21. 			r=m-1;
  22. 		}
  23. 	}
  24. 	//この関数の内側だけを書く
  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 5268KB
comments (?)
stdin
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4 7
3 5 7 9
stdout
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a[2] = 7
https://ideone.com/37p7x8
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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