#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define  BUF_SIZE  256


typedef  struct tag_StudentData
{
	double                  height;
	double                  weight;
	struct tag_StudentData  *next;
}	StudentData;

StudentData  StudentDataRoot = { 0, 0, NULL};


double  InputNumber(const char *prompt)
{
	char    buf[BUF_SIZE];
	double  ret;
	for(; ; )
	{
		printf("%sを入力してください: ", prompt);
		if(fgets(buf, sizeof(buf), stdin) == NULL)
			return -1;
		else if(sscanf(buf, "%lf", &ret) == 1)
			break;
		puts("数字で入力してください");
	}
	return ret;
}

void  InputStudentData()
{
	StudentData  *sd = &StudentDataRoot;
	while(sd->next != NULL)
		sd = sd->next;
	if((sd->next = (StudentData *)malloc(sizeof(StudentData))) == NULL)
	{
		perror("メモリが足りません");
		return;
	}
	sd = sd->next;
	sd->height = InputNumber("身長");
	sd->weight = InputNumber("体重");
	sd->next   = NULL;
}

void  PrintAverageHeight()
{
	int          Count = 0;
	double       TotalHeight = 0;
	StudentData  *sd = &StudentDataRoot;
	while(sd->next != NULL)
	{
		sd = sd->next;
		++Count;
		TotalHeight += sd->height;
	}
	if(Count < 1)
		puts("データがありません");
	else
		printf("平均身長=%.1f\n", TotalHeight / Count);
}

void  PrintAverageWeight()
{
	int          Count = 0;
	double       TotalWeight = 0;
	StudentData  *sd = &StudentDataRoot;
	while(sd->next != NULL)
	{
		sd = sd->next;
		++Count;
		TotalWeight += sd->weight;
	}
	if(Count < 1)
		puts("データがありません");
	else
		printf("平均体重=%.1f\n", TotalWeight / Count);
}

void  PrintAllData()
{
	StudentData  *sd = &StudentDataRoot;
	if(sd->next == NULL)
	{
		puts("データがありません");
		return;
	}
	puts("身長  体重");
	while((sd = sd->next) != NULL)
		printf("%5.1f %5.1f\n", sd->height, sd->weight);
}

void  DeleteAllData(StudentData *sd)
{
	if(sd == NULL)
		return;
	DeleteAllData(sd->next);
	free(sd);
}

int main(void)
{
	for(; ; )
	{
		int  innum;
		puts(
			"\n"
			"1: 生徒データの入力\n"
			"2: 平均身長の表示\n"
			"3: 平均体重の表示\n"
			"4: データ表の表示\n"
			"5: データの全消去\n"
			"\n"
			"0: プログラムの終了\n"
		);
		innum = (int)InputNumber("番号");
		if(innum < 0)
			goto ClearData;
		switch(innum)
		{
			case 1:
				InputStudentData();
				break;
			case 2:
				PrintAverageHeight();
				break;
			case 3:
				PrintAverageWeight();
				break;
			case 4:
				PrintAllData();
				break;
			case 5:
				DeleteAllData(StudentDataRoot.next);
				StudentDataRoot.next = NULL;
				break;
			case 0:
				goto ClearData;
		}
	}
ClearData:
	DeleteAllData(StudentDataRoot.next);
	return 0;
}