13 bài cơ bản sử dụng kĩ thuật dệ quy và kĩ thuật bắt phím

// dequy.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "stdio.h"
#include "conio.h"
#include "math.h"
#include "stdlib.h"
int s1(int n);
int s2(int n);
int s3(int n);
float s4(int n);
float s5(int n);
float s6(int n);
long t(int n);
float s8(int n);
long s9(int n);
int tich(int n);
float s10(int n);
int s11(int n);
int s12(int n);
long s13(int n);
//-------------------------------------------------------------
int main()
{  int n,maphim;
  printf("----------------huong dan su dung-------------");
  printf("\n\nnhan tu 1=>9 de chay tu bai 1 den bai 9");
  printf("\n\nnhan Shift+1,2 hay 3 de chay bay 11,12 hay 13");
  printf("\n\nnhan shift+0 de chay bai 10");
  printf("\n\nnhan thanh tasbar de xoa ma hinh");
  printf("\n\nnhan Esc de thoat chuong trinh");
  printf("\n\n--------------------------------------------");
  printf("\n\nMoi ban nhap n:");
  scanf("%d",&n);
  /*printf("\n\n_______________________");
  printf("\n\n***S=1+2+3+...+n");
  printf("\n\nTong s1=%d",s1(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+3+5+...+2n-1");
  printf("\n\nTong s2=%d",s2(n));
  printf("\n\n_______________________");
  printf("\n\n***S=2+4+6+...+2n");
  printf("\n\nTong s3=%d",s3(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+1/2+1/3+...+1/n");
  printf("\n\nTong s4=%.2f",s4(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+1/2+1/4+...+1/2n");
  printf("\n\nTong s5=%.2f",(s5(n)+1));
  printf("\n\n_______________________");
  printf("\n\n***S=1+1/3+1/5+...+1/2n-1");
  printf("\n\nTong s6=%.2f",s6(n));
  printf("\n\n_______________________");
  printf("\n\n***T=1*2*3*...*n");
  printf("\n\nTich T=%d",t(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1/2+2/3+3/4+...+n/n+1");
  printf("\n\nTong s8=%.2f",s8(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+2!+3!+...+n!");
  printf("\n\nTong S9=%d",s9(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+1/2!+1/3!+...+1/n!");
  printf("\n\nTong S10=%.2f",s10(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1^2+2^2+3^2+...+n^2");
  printf("\n\nTong S11=%d",s11(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1^2-2^2+3^2-...+(-1)^(n-1)*n^2");
  printf("\n\nTong s12=%d",s12(n));
  printf("\n\n_______________________");
  printf("\n\n***S=1+2^2+3^3+...+n^n");
  printf("\n\nTong s13=%d",s13(n));
  getch();*/
 while(!kbhit())
 {  maphim=getch();
  switch(maphim)
  {  case 49://1
      printf("\n\n_______________________");     
      printf("\n\n***S=1+2+3+...+n");
      printf("\n\nTong s1=%d",s1(n));break;
    case 50://2
      printf("\n\n_______________________");
      printf("\n\n***S=1+3+5+...+2n-1");
      printf("\n\nTong s2=%d",s2(n));break;
    case 51://3
      printf("\n\n_______________________");
      printf("\n\n***S=2+4+6+...+2n");
      printf("\n\nTong s3=%d",s3(n));break;
    case 52://4
      printf("\n\n_______________________");
      printf("\n\n***S=1+1/2+1/3+...+1/n");
      printf("\n\nTong s4=%.2f",s4(n));break;
    case 53://5
      printf("\n\n_______________________");
      printf("\n\n***S=1+1/2+1/4+...+1/2n");
      printf("\n\nTong s5=%.2f",(s5(n)+1));break;
    case 54://6
      printf("\n\n_______________________");
      printf("\n\n***S=1+1/3+1/5+...+1/2n-1");
      printf("\n\nTong s6=%.2f",s6(n));break;
    case 55://7
      printf("\n\n_______________________");
      printf("\n\n***T=1*2*3*...*n");
      printf("\n\nTich T=%d",t(n));break;
    case 56://8
      printf("\n\n_______________________");
      printf("\n\n***S=1/2+2/3+3/4+...+n/n+1");
      printf("\n\nTong s8=%.2f",s8(n));break;
    case 57://9
      printf("\n\n_______________________");
      printf("\n\n***S=1+2!+3!+...+n!");
      printf("\n\nTong S9=%d",s9(n));break;
    case 27://ESC
      return 0;
    case 32://space
      system("cls");
      printf("----------------huong dan su dung-------------");
      printf("\n\nnhan tu 1=>9 de chay tu bai 1 den bai 9");
      printf("\n\nnhan Shift+1,2 hay 3 de chay bay 11,12 hay 13");
      printf("\n\nnhan shift+0 de chay bai 10");
      printf("\n\nnhan thanh tasbar de xoa ma hinh");
      printf("\n\nnhan Esc de thoat chuong trinh");
      printf("\n\n--------------------------------------------");
      printf("\n\nMoi ban nhap n:");
      scanf("%d",&n);break;
    case 33://!
      printf("\n\n_______________________");
      printf("\n\n***S=1^2+2^2+3^2+...+n^2");
      printf("\n\nTong S11=%d",s11(n));break;
    case 64://@
      printf("\n\n_______________________");
      printf("\n\n***S=1^2-2^2+3^2-...+(-1)^(n-1)*n^2");
      printf("\n\nTong s12=%d",s12(n));break;
    case 35://#
      printf("\n\n_______________________");
      printf("\n\n***S=1+2^2+3^3+...+n^n");
      printf("\n\nTong s13=%d",s13(n));
    case 41://)
      printf("\n\n_______________________");
      printf("\n\n***S=1+1/2!+1/3!+...+1/n!");
      printf("\n\nTong S10=%.2f",s10(n));
    }
 }
 return 0;
}
//--------------s1=1+2+3+....+n----------------------------------
int s1(int n)
{  if(n<=0) return 0;
 return (s1(n-1)+n);
}
//--------------s2=1+3+5+....+2n-1-------------------------------
int s2(int n)
{  if((2*n-1)<=0) return 0;
 return (s2(n-1)+2*n-1);
}
//--------------s3=0+2+4+6+...+2n--------------------------------
int s3(int n)
{  if((2*n)<0) return 0;
 return (s3(n-1)+2*n);
}
//--------------s4=1+1/2+1/3+...+1/n------------------------------
float s4(int n)
{  if(n<1) return 0;
  return (s4(n-1)+(float)1/n);
}
//--------------s5=1+1/2+1/3+...+1/n------------------------------
float s5(int n)
{  if(n<=0) return 0;
  return (s5(n-1)+(float)1/(2*n));
}
//--------------s6=1+1/3+1/5+...+1/(2n-1)-------------------------
float s6(int n)
{  if(n<=0) return 0;
  return (s6(n-1)+(float)1/(2*n-1));
}
//--------------T=1*2*3*.....*n------------------------------------
long t(int n)
{  if(n<=0) return 1;
  return (t(n-1)*n);
}
//-------------s8=1/2+2/3+3/4+...+n/n+1----------------------------
float s8(int n)
{  if(n<=0) return 0;
  return (s8(n-1)+(float)n/(n+1));
}
//------------s9=1+2!+3!+....+n!-----------------------------------
long s9(int n)
{  if(n<=0) return 0;
  return (s9(n-1)+t(n));
}
//-------------s10=1+1/2!+1/3!+...+1/n!----------------------------
float s10(int n)
{  if(n<=0) return 0;
  return (s10(n-1)+(float)1/t(n));
}
//--------------s11=1^2+2^2+3^2+...+n^2-----------------------------
int s11(int n)
{  if(n<=0) return 0;
  return (s11(n-1)+(n*n));
}
//-------------s12=1^2-2^2+3^2-...+(-1)^n-1*n^2---------------------
int s12(int n)
{  if(n<=0) return 0;
  return (s12(n-1)+(pow(-1,n-1)*(n*n)));
}
//--------------s13=1+2^2+3^3+...+n^n-------------------------------
long s13(int n)
{  if(n<=0) return 0;
  return (s13(n-1)+pow(n,n));
}