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

main()
{
	int choose;
	char ans;

	printf("\n***************************************************");
	printf("\n* Student Name: Dinh Nguyen Anh Tuan              *");
	printf("\n* Please select the number for appropriate tasks  *");
	printf("\n*     1.Quit program                              *");
	printf("\n*     2.Question 2                                *");
	printf("\n*     3.Question 3                                *");
	printf("\n*     4.Question 4                                *");
	printf("\n***************************************************");


	printf("\n\nSelect your number: ");
	scanf("%d",&choose);

	switch(choose)
	{
		case 1:
			exit(0);
		case 2:
			_flushall();
			question2();
			break;
		case 3:
			_flushall();
			question3();
			break;
		case 4:
			_flushall();
			question4();
			break;
	}
}

question2()
{
	char num[100];
	int digits;
	int i;
	int dem;
	dem=0;
	printf("\n********Counting the digits of a number Program***********");
	printf("\nPlease enter a number: ");
	scanf("%s",&num);

		for(i=0;i<strlen(num);i++)
		{
			if(isdigit(num[i]) == 0) // isdigit = 0 nghia la num[i] ko phai chu so
			{
				printf("Invalid number");
				break;
			}
			dem++;
		}
		printf("\nThe number has %d digits",dem);




}

question3()
{
	char str[100];
	int i;
	int dem;
	dem=0;

	printf("\nEnter a string of characters: ");

	gets(str);

	//So luong cua tu trong chuoi
	for(i=0;i<strlen(str);i++)
	{
		if(str[i] ==' ')
		{
			dem++;
		}
	}
	printf("\nThe string has %d words",dem+1);

	//Moi tu o 1 hang trong chuoi
	printf("\nThe string with each word on a different line: \n");

	for(i=0;i<strlen(str);i++)
	{
		if(str[i] ==' ')
		{
			printf("\n");
		}
		else
		{
			printf("%c",str[i]);
		}
	}

	//Dao nguoc chuoi va xuat ra
	printf("\nThe string in reversed order of characters: \n");

	for(i=strlen(str);i>=0;i--)
	{
		printf("%c",str[i]);
	}
}

question4()
{

	struct detailStudent
	{
		char name[50];
		float csharp_mark;
		float java_mark;
		float english_mark;

	}Student[100];

	int n;
	int i;
	float total;
	float average;

		printf("\nEnter a number of students: ");
		scanf("%d",&n);
		//n tu 1-100
		while(n<1 || n>100)
		{
			printf("\nThe user must enter the appropriate number to continue");
			printf("\nEnter a number of students: ");_flushall();
			scanf("%d",&n);_flushall();
		}

		//Nhap thong tin hoc sinh
		printf("\nEnter the datas for each student: ");

		for(i=0;i<n;i++)
		{
			printf("\nEnter the detail of student %d",i+1);
			printf("\nName: ");_flushall();
			gets(Student[i].name);
			printf("\nC Sharp Mark: ");_flushall();
			scanf("%f",&Student[i].csharp_mark);
			printf("\nJava Mark: ");_flushall();
			scanf("%f",&Student[i].java_mark);
			printf("\nEnglish Mark: ");_flushall();
			scanf("%f",&Student[i].english_mark);

		}

		//Xuat thong tin hoc sinh
		for(i=0;i<n;i++)
		{
			printf("\n---------Detail of student %d-----------",i+1);
			printf("\nName: %s",Student[i].name);
			printf("\nC Sharp Mark: %.2f",Student[i].csharp_mark);
			printf("\nJava Mark: %.2f",Student[i].java_mark);
			printf("\nEnglish Mark: %.2f",Student[i].english_mark);

			//Tong diem
			printf("\nTotal Mark: %.2f",Student[i].csharp_mark+Student[i].java_mark+Student[i].english_mark);

			//Diem trung binh
			printf("\nAverage Mark: %.2f",(Student[i].csharp_mark+Student[i].java_mark+Student[i].english_mark)/4);
		}

}