C语言必背18个经典程序

#include "stdio.h"
main()
{int i,j,result;
 for(i=1;i<10;i++)
   {for(j=1;j<10;j++)
      {
         result=i*j;
         printf("%d*%d=%-3d",i,j,result);/*-3d表示左对齐，占3位*/
      }
     printf("\n");/*每一行后换行*/
   }
}

main()
{
long f1,f2;
int i;
f1=f2=1;
for(i=1;i<=20;i++)
  { printf("%12ld%12ld",f1,f2);
    if(i%2==0) printf("\n");/*控制输出，每行四个*/
     f1=f1+f2;/*前两个月加起来赋值给第三个月*/
    f2=f1+f2; /*前两个月加起来赋值给第三个月*/
   }
}

#include "math.h"
main()
{
  intm,i,k,h=0,leap=1;
 printf("\n");
 for(m=101;m<=200;m++)
   {k=sqrt(m+1);
    for(i=2;i<=k;i++)
      if(m%i==0)
         {leap=0;break;}
      if(leap)    /*内循环结束后，leap依然为1，则m是素数*/
         {printf("%-4d",m);h++;
          if(h%10==0)
               printf("\n");
         }
    leap=1;
   }
  printf("\nThetotal is %d",h);
}

main()
{
 static int k[10];
  inti,j,n,s;
 for(j=2;j<1000;j++)
    {
    n=-1;
    s=j;
    for(i=1;i<j;i++)
      {if((j%i)==0)
         {  n++;
             s=s-i;
            k[n]=i;
         }
      }
 if(s==0)
  {printf("%d is a wanshu: ",j);
   for(i=0;i<n;i++)
       printf("%d,",k[i]);
   printf("%d\n",k[n]);
   }
}
}

main()
{ int  a[4][4],b[4][4],i,j;       /*a存放原始数组数据，b存放旋转后数组数据*/
  printf("input 16 numbers: ");
/*输入一组数据存放到数组a中，然后旋转存放到b数组中*/
  for(i=0;i<4;i++)
      for(j=0;j<4;j++)
      { scanf("%d",&a[i][j]);
         b[3-j][i]=a[i][j];
       }
   printf("arrayb:\n");
  for(i=0;i<4;i++)
     {  for(j=0;j<4;j++)
        printf("%6d",b[i][j]);
        printf("\n");
      }
}

main()
{int i,j,a[6][6];
 for(i=0;i<=5;i++)
 {a[i][i]=1;a[i][0]=1;}
 for(i=2;i<=5;i++)
   for(j=1;j<=i-1;j++)
    a[i][j]=a[i-1][j]+a[i-1][j-1];
 for(i=0;i<=5;i++)
   {for(j=0;j<=i;j++)
       printf("%4d",a[i][j]);
    printf("\n");}
}

#include <stdio.h>
#include <stdlib.h>
main()
{ float a[4][5],sum1,sum2;
  inti,j;
 for(i=0;i<3;i++)
   for(j=0;j<4;j++)
     scanf("%f",&a[i][j]);
 for(i=0;i<3;i++)
  {sum1=0;
   for(j=0;j<4;j++)
     sum1+=a[i][j];
     a[i][4]=sum1/4;
  }
 for(j=0;j<5;j++)
 {  sum2=0;
    for(i=0;i<3;i++)
      sum2+=a[i][j];
      a[3][j]=sum2/3;
   }
  for(i=0;i<4;i++)
  {  for(j=0;j<5;j++)
     printf("%6.2f",a[i][j]);
     printf("\n");
   }
}

#include <string.h>
main()
{ char  c[200],c1;
  int i,j,k;
  printf("Enter a string: ");
  scanf("%s",c);
  k=strlen(c);
  for (i=0,j=k-1;i<k/2;i++,j--)
    {  c1=c[i];c[i]=c[j];c[j]=c1;  }
  printf("%s\n",c);        
}

void invert(char *s)
{int i,j,k;
 char t;
 k=strlen(s);
 for(i=0,j=k-1;i<k/2;i++,j--)
 {  t=*(s+i); *(s+i)=*(s+j);  *(s+j)=t; }
}
main()
{FILE *fp;
char str[200],*p,i,j;
if((fp=fopen("p9_2.out","w"))==NULL) 
     { printf("cannot open thefile\n");
       exit(0);                       
     }
  printf("input str:\n");
gets(str);
  printf(“\n%s”,str);
fprintf(fp,“%s”,str);
invert(str);
   printf(“\n%s”,str);
fprintf(fp,“\n%s”,str);
 fclose(fp);
}

#include <stdio.h>
main()
{ char  s[80],c;
  int  j,k;
  printf("\nEnter a string: ");
  gets(s);
  printf("\nEnter a character: ");
  c=getchar( );
  for(j=k=0;s[j]!= '\0';j++)
  if(s[j]!=c)
     s[k++]=s[j];
   s[k]='\0';
  printf("\n%s",s);
}

#include<stdio.h>
void sort(int *x,int n)
{
int i,j,k,t;
for(i=0;i<n-1;i++)
{
 k=i;
 for(j=i+1;j<n;j++)
  if(x[j]>x[k]) k=j;
   if(k!=i)
   {
   t=x[i];
   x[i]=x[k];
   x[k]=t;
   }
}
}
void main()
{FILE *fp;
    int *p,i,a[10];
    fp=fopen("p9_1.out","w");                      
   p=a;
printf("Input 10 numbers:");
for(i=0;i<10;i++)
 scanf("%d",p++);
p=a;
sort(p,10);
for(;p<a+10;p++)
 { printf("%d ",*p);
       fprintf(fp,"%d ",*p);  }
       system("pause");
   fclose(fp);
}

   main()
   {  inta[10]={0,12,17,20,25,28,30};       /*a[0]为工作单元，从a[1]开始存放数据*/
      int  x , i, j=6;                         /*j为元素个数*/
      printf("Enter a number: "); 
      scanf("%d",&x);
      a[0]=x;
      i=j;                              /*从最后一个单元开始*/
      while(a[i]>x)
      {  a[i+1]=a[i]; i--;    }  /*将比x大的数往后移动一个位置*/
      a[++i]=x;
      j++;                       /*插入x后元素总个数增加*/
      for(i=1;i<=j;i++) printf("%8d",a[i]);
      printf("\n");
}

#include<stdio.h>
replace(char*s,char c1,char c2)
{while(*s!='\0')
   {  if(*s==c1)
         *s=c2;
         s++; 
   }
}
main()
{ FILE *fp;
  char str[100],a,b;
  if((fp=fopen("p10_2.out","w"))==NULL)
      { printf("cannot open thefile\n");
       exit(0);                     }
   printf("Enter a string:\n");
    gets(str);
    printf("Enter a&&b:\n");
    scanf("%c,%c",&a,&b);
printf("%s\n",str);
fprintf(fp,"%s\n",str);
replace(str,a,b);
printf("Thenew string is----%s\n",str);
fprintf(fp,"Thenew string is----%s\n",str);
fclose(fp);
}

main()
{chars1[6]="thisis";char s2[5]="is";
printf("%d\n",search(s1,s2));
system("pause");
}
int search(chars1[],char s2[])
{inti=0,j,len=strlen(s2);
while(s1[i]){
 for(j=0;j<len;j++)
 if(s1[i+j]!=s2[j]) break;
 if(j>=len)return i;
 else i++;
 }
return -1;
}

struct student
{
 int num;
 char *name;
char sex;
int age;
}stu[5]={{1001,"lihua",'F',18},{1002,"liuxing",'M',19},{1003,"huangke",'F',19},{1004,"fengshou",'F',19},{1005,"Wangming",'M',18}};
main()
{int i;
struct student *ps;
printf("Num \tName\t\t\tSex\tAge\t\n");   
/*用指针变量输出结构体数组元素。*/
for(ps=stu;ps<stu+5;ps++)
printf("%d\t%-10s\t\t%c\t%d\t\n",ps->num,ps->name,ps->sex,ps->age);
/*用数组下标法输出结构体数组元素学号和年龄。*/
for(i=0;i<5;i++)
printf("%d\t%d\t\n",stu[i].num,stu[i].age);
}

#define NULL 0
struct student
{
int num;
char *name;
int age ;
struct student*next;
};
void main()
{
struct studenta,b,c,*head,*p;
a.num=1001;a.name="lihua"; a.age=18; /*  对结点成员进行赋值  */
b.num=1002;b.name="liuxing"; b.age=19;
c.num=1003;c.name="huangke"; c.age=18;
head=&a;                           /*  建立链表，a为头结点  */
a.next=&b;
b.next=&c;
c.next=NULL;
p=head;                            /*  输出链表  */
do{
printf("%5d,%s,%3d\n",p->num,p->name,p->age);
p=p->next;
}while(p!=NULL);
}

#include<stdio.h>
#include<string.h>
#include<string.h>
main()
{ char s[100];
  int i,j,n;
  printf("输入字符串：\n");
  gets(s);
  n=strlen(s);
  for(i=0,j=n-1;i<j;i++,j--)
    if(s[i]!=s[j])   break;
  if(i>=j) printf("是回文串\n");
  else    printf("不是回文串\n");
}

#include<stdio.h>
void fun(inta[],int n)
{int i,j,t;
for(i=0;i<=n-1;i++)
  for(j=0;j<i;j++)
    if(a[j]>a[j+1]){t=a[j];a[j]=a[j+1];a[j+1]=t;}
}
main()
{inta[10]={12,45,7,8,96,4,10,48,2,46},n=10,i;
FILE *f;
if((f=fopen("myf2.out","w"))==NULL)
   printf("open file myf2.outfailed!\n");
fun(a,10);
for(i=0;i<10;i++)
   {printf("%4d",a[i]);
    fprintf(f,"%4d",a[i]);
   }
fclose(f);
}

#include<stdio.h>
doublecountpi(double eps)               /*eps为允许误差*/
  {
    int m=1;
     double temp=1.0,s=0;
     while(temp>=eps)
     { s+=temp;
        temp=temp*m/(2*m+1);
        m++;
     }
     return(2*s);
  }
main()
{FILE *fp;
     double eps=1e-5,pi;
    if((fp=fopen("p7_3.out","w"))==NULL) 
   { printf("cannot open thefile\n");
     exit(0);                      
   }
   pi= countpi(eps);
   printf("pi=%lf\n",pi);
fprintf(fp,"pi=%lf\n",pi);
fclose(fp);
}