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]為工作單元，從a[1]開(kāi)始存放數(shù)據(jù)*/
      int  x , i, j=6;                         /*j為元素個(gè)數(shù)*/
      printf("Enter a number: "); 
      scanf("%d",&x);
      a[0]=x;
      i=j;                              /*從最后一個(gè)單元開(kāi)始*/
      while(a[i]>x)
      {  a[i+1]=a[i]; i--;    }  /*將比x大的數(shù)往后移動(dòng)一個(gè)位置*/
      a[++i]=x;
      j++;                       /*插入x后元素總個(gè)數(shù)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");   
/*用指針變量輸出結(jié)構(gòu)體數(shù)組元素。*/
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);
/*用數(shù)組下標(biāo)法輸出結(jié)構(gòu)體數(shù)組元素學(xué)號(hào)和年齡。*/
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; /*  對(duì)結(jié)點(diǎn)成員進(jìn)行賦值  */
b.num=1002;b.name="liuxing"; b.age=19;
c.num=1003;c.name="huangke"; c.age=18;
head=&a;                           /*  建立鏈表，a為頭結(jié)點(diǎn)  */
a.next=&b;
b.next=&c;
c.next=NULL;
p=head;                            /*  輸出鏈表  */
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("輸入字符串：\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為允許誤差*/
  {
    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);
}