数据结构串的操作实例及相关代码分析

#include <stdio.h> 
#include <stdlib.h> 
 
#define MAXSIZE 20 
char *String_Create();         //创建串 
int String_Length(char *s);       //求串长 
void String_Show(char *s);       //输出串 
char *String_Copy(char *d, char *s);  //串复制 
char *String_Connect(char *d, char *s); //串连接 
char *String_SubStr(char *d, char *s, int pos, int len);  //求子串 
int String_Compare(char *d, char *s);  //串比较 
char *String_Insert(char *d, char *s, int pos);   //串插入 
char *String_Delete(char *d, int pos, int len);   //串删除 
int String_Index(char *d, char *s, int pos);    //串匹配 
 
int main(void) 
{ 
  int choice; 
  char *str, *c; 
  int ans, pos, len; 
 
  c = (char*)malloc(sizeof(MAXSIZE)); 
  printf("请输入一串字符串(小于10个字符):\n"); 
  str = String_Create(); 
   
  while(1) 
  { 
    printf("***************************\n"); 
    printf("字符串操作练习:\n"); 
    printf("1.求串长\n"); 
    printf("2.串复制\n"); 
    printf("3.串连接\n"); 
    printf("4.求子串\n"); 
    printf("5.比较串\n"); 
    printf("6.串插入\n"); 
    printf("7.串删除\n"); 
    printf("8.串定位\n"); 
    printf("9.串输出\n"); 
    printf("10.退出程序\n"); 
     
    printf("输入选择:\n"); 
    scanf("%d", &choice); 
    getchar(); 
 
    switch(choice) 
    { 
    case 1: 
      ans = String_Length(str); 
      printf("串的长度为%d\n", ans); 
      break; 
    case 2: 
      c = String_Copy(c, str); 
      printf("目标字符串为:\n"); 
      String_Show(c); 
      break; 
    case 3: 
      printf("输入字串(小于10个字符)\n"); 
      gets(c); 
      c = String_Connect(c, str); 
      printf("新的字符串为\n"); 
      String_Show(c); 
      break; 
    case 4: 
      printf("输入你想求子串所在位置及长度\n"); 
      scanf("%d %d", &pos, &len); 
      c = String_SubStr(c, str, pos, len); 
      if(c == NULL) 
        printf("求子串失败！\n"); 
      else 
      { 
        printf("所求子串为:\n"); 
        String_Show(c); 
      } 
      break; 
    case 5: 
      printf("输入字串:\n"); 
      gets(c); 
      ans = String_Compare(c, str); 
      if(ans>0) 
        printf("首字符串大\n"); 
      else if(ans<0) 
        printf("第二个字符串大\n"); 
      else 
        printf("两字符串相等\n"); 
      break; 
    case 6: 
      printf("输入需在主串中插入的字串\n"); 
      gets(c); 
      printf("输入插入的位置:\n"); 
      scanf("%d", &pos); 
      str = String_Insert(str, c, pos); 
      printf("新的字符串为:\n"); 
      String_Show(str); 
      break; 
    case 7: 
      printf("输入删除子串的起始位置及长度\n"); 
      scanf("%d %d", &pos, &len); 
      str = String_Delete(str, pos, len); 
      break; 
    case 8: 
      printf("输入要定位的子串:\n"); 
      gets(c); 
      ans = String_Index(str, c, 1); 
      printf("定位的结果为%d\n", ans); 
      break; 
    case 9: 
      String_Show(str); 
      break; 
    case 10: 
      return 0; 
      break; 
    default: 
      printf("选择无效!\n"); 
      break; 
    } 
  } 
  return 1; 
} 
 
//创建串 
char *String_Create() 
{ 
  char *s, ch; 
  int i = 0; 
 
  s = (char*)malloc(MAXSIZE); 
  ch = getchar(); 
  while(ch != '#') 
  { 
    *(s+i) = ch; 
    i++; 
    ch = getchar(); 
  } 
  if(i > MAXSIZE/2) 
    printf("输入长度大于10!\n"); 
  else 
    *(s+i) = '\0'; 
  return s; 
} 
 
//求串长 
int String_Length(char *s) 
{ 
  int l=0; 
 
  while(*s != '\0') 
  { 
    l++; 
    s++; 
  } 
 
  return l; 
} 
 
//串的复制 
char *String_Copy(char *d, char *s) 
{ 
  char *c; 
 
  c = d; 
  while((*d++=*s++)!='\0'); 
 
  return c; 
} 
 
//串连接 
char *String_Connect(char *d, char *s) 
{ 
  char *c; 
  int l, i=0;; 
 
  c = d; 
  l = String_Length(d); 
  d = d + l; 
  while((*d++ = *s++) != '\0');    //串连接 
 
  return c; 
} 
 
//求子串 
char *String_SubStr(char *d, char *s, int pos, int len) 
{ 
  char *c1, *c2=NULL; 
  int l, i; 
   
  c2 = (char*)malloc(MAXSIZE/2); 
 
  c1 = s; 
  d = c2; 
  l = String_Length(s); 
 
  if(pos>l || pos<1)      //输入位置非法 
    return NULL; 
  if(len<0)          //输入长度非法 
    return NULL; 
  c1 = c1 + pos - 1; 
   
  for(i=1; i<=len && *c1 != '\0'; i++) //求字串 
  { 
    *c2++ = *c1++; 
  } 
  *c2 = '\0';         //不要忘记结尾符号 
   
  return d; 
} 
 
//串比较 
int String_Compare(char *d, char *s) 
{ 
  char *c1, *c2; 
 
  c1 = d; 
  c2 = s; 
 
  while(*c1 != '\0' || *c2 != '\0') 
  { 
    if(*c1 > *c2) 
      return 1; 
    else if(*c1 < *c2) 
      return -1; 
    c1++; 
    c2++; 
  } 
  if(*c1 == '\0' && *c2 == '\0')   //两个字符处都结束时，则两字符串相等 
    return 0; 
  else if(*c2 == '\0')        //第二个字符串先结束，则第一个字符串大 
    return 1; 
  else 
    return -1; 
} 
 
//插入串 
char *String_Insert(char *d, char *s, int pos) 
{ 
  int i, ld,ls; 
  char *c1, *c2; 
 
  c1 = d; 
  c2 = s; 
 
  ld = String_Length(d); 
  ls = String_Length(s); 
 
  for(i=ld; i>=pos-1; i--)   //字符串后移，留出待插字符串位置 
    *(c1 + ls + i) = *(c1 + i);  
  for(i=pos; i<=pos+ls-1; i++) //插入子字符串 
    *(c1 + i - 1) = *c2++; 
  *(c1 + ld + ls) = '\0';     //最后的结尾符号不能忘掉 
 
  return d; 
} 
 
//串删除 
char *String_Delete(char *d, int pos, int len) 
{ 
  int i, l; 
 
  l = String_Length(d); 
  if(pos + len > l)        //如果删除长度大于字串开始位置后面的长度，则只保留主串前面字符 
    *(d + pos -1) = '\0'; 
  else 
  { 
    for(i=pos+len-1; i<=l; i++) 
      *(d + i - len) = *(d + i); 
    *(d + l - len) = '\0';   //结束字符 
  } 
 
  return d; 
} 
 
//子串定位 
int String_Index(char *d, char *s, int pos) 
{ 
  int i = pos - 1, j = 0, ld, ls, b=0; 
 
  ld = String_Length(d); 
  ls = String_Length(s); 
  while(i < ld && j<ls) 
  { 
    if(*(d+i) == *(s+j))  //当前字符相等，则继续匹配 
    { 
      i++; 
      j++; 
    } 
    else          //下一趟匹配 
    { 
      i = i - j + 1; 
      j = 0; 
    } 
  } 
  if(j == ls)     //匹配成功 
    return (i - ls + 1); 
  else 
    return 0; 
} 
 
//输出串 
void String_Show(char *s) 
{ 
  while(putchar(*s++)); 
  printf("\n"); 
}