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/*[Ｃ言語]サンプルプログラム集　２分探索法ソース３*/
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#include <stdio.h>

struct STUDENT{
	char name[128];
	int score;
};

int my_binary2(struct STUDENT* ,int,int,int);

int main(){
	int result = 0;
	int target = 52;
	int j = 0;

	struct STUDENT student[10] = {
		{"tanaka",5},
		{"suzuki",7},
		{"satou",13},
		{"saitou",18},
		{"watanabe",27},
		{"aoki",32},
		{"inoue",38},
		{"koike",52},
		{"wada",60},
		{"ueno",78},
	};

	result = my_binary2(student,target,0,9);	

	printf("配列の内容\n");

	for(j=0;j<10;j++){
		printf("名前 %s:得点 %d\n",student[j].name,student[j].score);
	}

	printf("\n探す対象 = %d\n\n",target);
	
	if(result == -1){
		printf("見つかりませんでした！\n");
	}
	else{
		printf("添え字番号%d番目で見つかりました！\n",result);
		printf("名前 %s:得点 %d\n",student[result].name,student[result].score);
	}

	return 0;
}

int my_binary2(struct STUDENT* ary,int target,int index_head,int index_tail){

	int center = (index_head + index_tail) / 2;

	while(1){
		if((ary + center)->score == target || index_head > index_tail){
			break;
		}
		else if((ary + center)->score < target){
			index_head = center + 1;
		}
		else{
			index_tail = center - 1;
		}
		center = (index_head + index_tail) / 2;
	}

	if(index_head > index_tail){
		return -1;
	}
	else{
		return center;
	}
}
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