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

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