串的插入，删除，定位，连接等操作

#include<stdlib.h>
#include<iostream>


#define MAXLEN 20
#define TRUE 1
#define FALSE 0

using namespace std;

typedef struct SString{
char ch[MAXLEN];
int len;
}SString;

//初始化串
void StrInit(SString *S)
{
char data;
S->len=0;
cout<<"请输入串，按#结束\n";
cin>>data;
while(data!='#')
{
   S->ch[S->len]=data;
   S->len++;
   cin>>data;
}
S->ch[S->len]='\0';
}

//将T串插入到S串pos开始，S串后移
int StrInsert(SString *S,int pos,SString *T)
{
int i;
if(pos<0||pos>S->len)return FALSE;
if(S->len+T->len<=MAXLEN){
   for(i=S->len+T->len-1;i>=T->len+pos;i--)
    S->ch[i]=S->ch[i-T->len];
   for(i=0;i<T->len;i++)
    S->ch[pos+i]=T->ch[i];
   S->len+=T->len;
}
else if(pos+T->len<=MAXLEN){
   for(i=MAXLEN-1;i>=pos+T->len;i--)
    S->ch[i]=S->ch[i-T->len];
   for(i=0;i<T->len;i++)
    S->ch[i+pos]=T->ch[i-T->len];
   S->len=MAXLEN;
}
else{
   for(i=pos;i<MAXLEN;i++)
    S->ch[i]=T->ch[i-pos];
   S->len=MAXLEN;
}
return TRUE;
}

//删除S串中从pos开始的len个字符
int StrDel(SString *S,int pos,int len)
{
int i;
if(pos<0||pos>(S->len-len))return FALSE;
for(i=pos+len;i<S->len;i++)
   S->ch[pos++]=S->ch[i];
S->len=S->len-len;
return TRUE;
}

//将串T拷贝到串S
int StrCpy(SString *S,SString *T)
{
int i;
for(i=0;i<T->len;i++){
   S->ch[i]=T->ch[i];
}
S->len=T->len;
return TRUE;
}

//判断串是否为空，为空返回TRUE,否则返回FALSE
int StrEmpty(SString *S)
{
int flag;
return S->len==0?flag=TRUE:flag=FALSE;
}

//串比较函数
int StrCompare(SString *S,SString *T)
{
int i=0;
if(S->len!=T->len)return FALSE;
while(i<S->len)
{
   if(S->ch[i]!=T->ch[i])
    return FALSE;
}
return TRUE;
}

//求串的长度
int StrLen(SString *S)
{
return S->len;
}

//清空串
int StrClear(SString *S)
{
S->len=0;
return TRUE;
}


//将串T连接到串S后
int StrCat(SString *S,SString *T)
{
int i;
if(S->len+T->len<=MAXLEN){
   for(i=0;i<T->len;i++)
    S->ch[S->len+i]=T->ch[i];
   S->len+=T->len;
}
else if(S->len<MAXLEN){
   for(i=S->len;i<MAXLEN;i++)
    S->ch[i]=T->ch[i-S->len];
   S->len=MAXLEN;
}
else{
   return FALSE;
}
return TRUE;

}

//求串S中pos开始， 串T第一次出现的位置
int StrIndex(SString *S,int pos,SString *T)
{
int i,j;
if(T->len==0)return FALSE;
i=pos;j=0;
while(i<S->len&&j<T->len)
{
   if(S->ch[i]==T->ch[j]){i++;j++;}
   else{
    i=i-j+1;
    j=0;
   }
}
if(j>=T->len)return i-j;
else return 0;
}

void StrOutput(SString *S)
{
int i;
for(i=0;i<S->len;i++)
   i!=S->len-1?cout<<S->ch[i]<<" ":cout<<S->ch[i]<<"\n";
}


int main()
{
char cmd;int pos;
int len;int index;
do{
   SString *S=(SString *)malloc(sizeof(SString));
   SString *T=(SString *)malloc(sizeof(SString));
   StrInit(S);StrInit(T);
   cout<<"求串T在串S中从pos开始第一次出现的位置,输入pos\n";
   cin>>pos;
   index=StrIndex(S,pos,T);
   cout<<"位置是"<<index<<"\n";
   cout<<"输入插入到串S的位置pos\n";
   cin>>pos;
   StrInsert(S,pos,T);
   StrOutput(S);
   cout<<"输入要删除串S中开始的序号pos及字符长度len\n";
   cin>>pos>>len;
   StrDel(S,pos,len);
   StrOutput(S);

   cout<<"输入y/Y继续，其他退出\n";
   cin>>cmd;
}while(cmd=='y'||cmd=='Y');
    return 0;

}