1. VIẾT HÀM S = 1 + ..... + (2*N + 1)

/* tinh tong day 1+3+5+....+(2*n+1) */

#include<conio.h>

#include<stdio.h>

//================================

int tong(int n)

{int i,s;

for(i=1,s=0;i<2*n+1;i+=2)/* hoac for(i=1,s=0;i<=s;i++)s=s+2*i+1; */

s=s+i;

return s;

}

//================================

void main()

{

clrscr();

int n,s;

char ch;

tiep: printf("

nhap n=");

scanf("%d",&n);

if (n<=0){printf ("

moi nhap lai n");goto tiep;}

s=tong(n);

printf (" tong cua dayla:%d",s);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

2. VIẾT HÀM TÍNH GIAI THỪA

#include<conio.h>

#include<stdio.h>

//==============================

unsigned long giaithua(int n)

{

int i;

unsigned long gt;

for (i=1,gt=1;i<=n;i++)

gt=gt*i;

return gt;

}

/*hoac su dung de quy :

long giaithua (int n)

{

iF (n==0) return 1;

return n*giaithua(n-1);

}

*/

//================================

void main()

{

clrscr();

int n;

char ch;

tiep: printf("

nhap n moi=");

scanf("%d",&n);

if (n<0){printf ("

moi nhap lai n");goto tiep;}

printf("

%d!=%lu",n,giaithua(n));

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

3. VIẾT HÀM ĐỔI THÀNH XÂU NHỊ PHÂN

#include<stdio.h>

#include<conio.h>

void chuyen (int n)

{

int i=0,j,a[50];

while (n!=0)

{

a[i]=n%2;

n=n/2;

i++;

}

j=i-1;

for(i=j;i>=0;i--)

printf("%d",a[i]);

}

void main ()

{

clrscr();

int n;

char ch;

printf("\t\t\t Chuyen doi thap phan sang nhi phan");

tiep:printf("

Ban hay nhap so can chuyen doi: ");

scanf("%d",&n);

if (n<0) goto tiep;

printf("

day nhi phan cua %d la:",n);

chuyen (n);

printf("

ban co muon tiep tuc c/k");

ch=getch();

if ((ch=='c')||(ch=='C')) goto tiep;

else printf("

cam on va tam biet");

}

4. VIẾT HÀM S = 1 +...... + 2*N

/* ham tinh tong 2+4+6+..........+2*n*/

#include<conio.h>

#include<stdio.h>

//------------------------------------------

int tong (int n)

{

int i,s;

for(i=1,s=0;i<=n;i++)

s=s+2*i;

return s;

}

//============================================

void main()

{ clrscr();

int n,s;

char ch;

tiep: printf("nhap n=");

scanf("%d",&n);

if (n<=0){printf ("moi nhap lai n");goto tiep;}

s=tong(n);

printf("tong cua day la:%d",s);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

5. BIẾN THÀNH XÂU HEXA

/*bai ni sua tap*/

#include <stdio.h>

void main()

{

unsigned number;

char hex[] = "0123456789ABCDEF";

printf("

Nhap vao mot gia tri nguyen duong 16 bit : ");

scanf("%u", &number);

printf("Gia tri Hex tuong ung = %c%c%c%c",

hex[number/0x1000], hex[(number/0x100)%0x10],

hex[(number/0x10)%0x10], hex[number%0x10]);

getch();

}

6. S = 1^3 + .... + N^3

/* tinh tong s = 1^3 + 2^3 + ... + n^3 */

#include<conio.h>

#include<stdio.h>

//=============================================

int tong(int n)

{

int i,s;

for(i=1,s=0;i<=n;i++)

s=s+i*i*i;

return s;

}

//============================================

main()

{

clrscr();

int n,s;

char ch;

tiep: printf("nhap n=");

scanf("%d",&n);

if (n<=0){printf ("

moi nhap lai n");goto tiep;}

s=tong(n);

printf("tong cua chuoi la:%d",s);

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

return 0;

}

7. TÍNH NGUYÊN TỐ CỦA MỘT SỐ NGUYÊN DƯƠNG

#include<conio.h>

#include<stdio.h>

int nguyento(int n)

{

int i;

for(i=2;i<=n/2;i++)

if(n%i==0)return 0;

return 1;

}

main()

{

clrscr();

int n;

char ch;

tiep: printf("nhap n=");

scanf("%d",&n);

if(n<=1)goto tiep;

if(nguyento(n)==1)

printf("%d la so nguyen to",n);

else

printf("%d khong la so nguyen to",n);

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

return 0;

}

8. S = 1*2*3 + ... + N*(N+1)*(N+3)

/* ham tinh tong 1*2*3+2*3*4+.........n*(n+1)*(n+2),*/

#include<conio.h>

#include<stdio.h>

//=========================================

int tong(int n)

{int s,i;

for (i=1,s=0;i<=n;i++)

s=s+i*(i+1)*(i+2);

return s;

}

//=======================================

main()

{

clrscr();

int n,s;

char ch;

tiep: printf("nhap n=");

scanf("%d",&n);

if (n<=0){printf ("moi nhap lai n");goto tiep;}

s=tong(n);

printf("tong cua day la:%d",s);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

return 0;

}

9. TÍNH HOÀN THIỆN

#include<conio.h>

#include<stdio.h>

int sht (int n)

{

int i,s;

s=0;

for (i=1;i<n-1;i++)

if (n%i==0)

s=s+i;

if (n==s)return 1;

return 0;

}

void main()

{

int n;

char ch;

tiep:printf("

moi nhap n=");

scanf ("%d",&n);

if (sht(n)==1)

printf("

%d la so hoan thien ",n);

else

printf("

%d la so khong hoan thien ",n);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

10. TÌM SỐ BÉ NHẤT

#include<stdio.h>

#include<conio.h>

float min (int a,int b,int c)

{

float min;

min=a;

if (min>b) min=b;

if (min>c) min=c;

return min;

}

main()

{

clrscr();

float a,b,c;

char ch;

tiep:printf("

nhap a,b,c =");

scanf("%f%f%f",&a,&b,&c);

printf("

so nho nhat trong 3 so la:%5.1f",min(a,b,c));

printf("

co muon tiep tuc khong c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf("

tam biet");

return 0;

}

11. VIẾT HÀM GIẢI PT BẬC 2

include<conio.h>

#include<stdio.h>

#include<math.h>

void ptb2(float a,float b,float c)

{

float x1,x2,delta;

if (a==0)

if (b==0)

if (c==0)

printf(" pt co vo so nghiem");

else

printf(" pt vo nghiem");

else

printf(" pt co nghiem la %5.2f",-c/b);

else

{

delta=(b*b-4*a*c);

if (delta<0)

printf("pt vo nghiem");

else

if(delta==0)

printf(" pt co nghiem la x=%5.2f",-b/2/a);

else

{

x1=(-b+sqrt(delta))/2/a;

x2=(-b-sqrt(delta))/2/a;

printf("pt co hai ngiem x1=%5.2f,x2=%5.2f",x1,x2);

}

}

}

main()

{

clrscr();

float a,b,c;

char ch;

tiep:printf ("

nhap he so a,b,c=");

scanf("%f%f%f",&a,&b,&c);

ptb2 (a,b,c);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

return 0;

}

12. 3 CẠNH TAM GIÁC

#include<conio.h>

#include<stdio.h>

//--------------------------

void kiemtra (int a,int b,int c)

{

if((a+b>c)&&(a+c>b)&&(b+c>a))

printf("abc la canh cua tam giac");

else

printf("abc khog phai la canh cua tam giac");

}

main()

{clrscr();

float a,b,c;

char ch;

tiep:printf("

nhap vao a,b,c");

scanf("%f%f%f",&a,&b,&c);

kiemtra (a,b,c);

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

return 0;

}

13. ĐẾM TỪ TRONG XÂU

#include<conio.h>

#include<stdio.h>

#include<string.h>

int dem (char a[])

{

int i,s=1;

for (i=0;i<strlen(a);i++)

if (a[i]==' ')

s=s+1;

return s;

}

void main()

{

clrscr();

char s[100],ch;

tiep:printf("

nhap xau can kiem tra: ");

gets (s);

printf("

so tu cua xau vua nhap la:%2.1d",dem(s));

printf("

ban co muong tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

14. TÍNH SỐ FIBONAXI THỨ N

#include<conio.h>

#include<stdio.h>

int fibonaxi(int n)

{

if((n==1)||(n==2)) return 1;

return (fibonaxi(n-2)+fibonaxi(n-1));

}

void main()

{

clrscr();

int n;

char ch;

tiep:printf("

nhap n=");

scanf("%d",&n);

if (n<=0) goto tiep;

printf("

so fibonaxi thu %2.1d la:%2.1d",n,fibonaxi(n));

printf ("

ban co muon tiep tuc c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf ("

cam on va tam biet");

}

15. ĐỔI CHỖ GIÁ TRỊ HAI BIẾN THỰC CHO NHAU

#include<conio.h>

#include<stdio.h>

void doicho(float *a,float *b)

{

float tg;

tg=*a;*a=*b;*b=tg;

}

main()

{

float x,y;

printf("nhap x,y=");

scanf("%f%f",&x,&y);

printf("

gia tri x,y truoc khi doi la:%5.2f,%5.2f",x,y);

doicho(&x,&y);

printf("

gia tri x,y sau khi doi la:%5.2f,%5.2f",x,y);

getch();

}

16. TÌM UCLN

#include<conio.h>

#include<stdio.h>

int uocchung (int a,int b)

{if(a==b) return a;

if(a>b) return uocchung(a-b,b);

return uocchung(a,b-a);

}

main()

{

clrscr();

int a,b;

nhap:printf("

nhap a,b=");

scanf("%d%d",&a,&b);

if((a<0)||(b<0)) goto nhap;

printf("

uoc chung lon nhat la:%d",uocchung(a,b));

getch();

}

17. TÍNH ĐỘ DÀI XÂU KÍ TỰ

#include<conio.h>

#include<stdio.h>

int dem(char a[])

{int i=0;

while (a[i]!=NULL)i++;

return i;

}

void main(void)

{

clrscr();

char s[20];

int t;

printf("

nhap chuoi:");

gets(s);

t=dem(s);

printf("

do dai xau s la :%d",t);

getch();

}

18. ĐẾM CHỮ SỐ IN HOA

#include<conio.h>

#include<stdio.h>

int demhoa (char a[])

{

int i=0,n=0;

while(a[i]!=NULL)

{

if((a[i]>='A')&&(a[i]<='Z'))

n++;

i++;

}

return n;

}

void main(void)

{

clrscr();

char s[20],ch;

int t;

tiep:printf("

nhap chuoi:");

gets(s);

t=demhoa(s);

printf("

so chu hoa la :%d",t);

printf("

ban co muon tiep tuc c/k");

ch=getch();

if ((ch=='c')||(ch=='C')) goto tiep;

else printf("

cam on va tam biet");

}

19. ĐỔI CHỮ IN HOA THÀNH CHỮ IN THƯỜNG

#include <stdio.h>

#include <string.h>

#include <ctype.h>

#include <conio.h>

void hoa(char *a)

{

for(int i=0;i<strlen(a);i++)

a[i]=toupper(a[i]);

}

void thuong(char *a)

{ hfghgfhfhfhfgh

for(int i=0;i<strlen(a);i++)

a[i]=tolower(a[i]);

}

main(void)

{

char s[200];

printf("Nhap vao 1 chuoi :");

fflush(stdin);

gets(s);

hoa(s);

printf("Chuoi viet hoa : %s",s);

thuong(s);

printf("

Chuoi viet thuong :%s",s);

getch();

}

20. PT BẬC NHẤT

#include<conio.h>

#include<stdio.h>

#include<math.h>

void ptb1(float a,float b)

{

if(a==0)

if(b==0)

printf("phuong trinh vo so ngiem");

else

printf("phuong trinh vo nghiem");

else

printf("phuogn trinh con nghiem x la:%5.2f",-b/2/a);

}

//-------------------------------------------

main()

{

clrscr();

float a,b;

char ch;

tiep:printf("nhap vap a,b=");

scanf("%f%f",&a,&b);

ptb1(a,b);

printf("

co muon tiep tuc khong c/k");

ch=getch();

if((ch=='c')||(ch=='C')) goto tiep;

else printf("

tam biet");

return 0;

}