串，模式匹配Index

1.串的顺序存储实现

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAXSIZE 40
#define OK 1
#define Status int
typedef char SString[MAXSIZE + 1];//0号单元存放串的长度

Status StrAssign(SString T, char *chars)//生成一个其值等于chars的子串
{
int i;
if (strlen(chars)>MAXSIZE) return 0;
else
{
T[0] = strlen(chars);
for (i = 1; i <= T[0]; i++)
T[i] = *(chars + i - 1);
return OK;
}
}
int StrLength(SString S)
{
return S[0];
}
int StrCompare(SString S, SString T)
{
int i;
for (i = 1; i <= S[0] && i <= T[0]; i++)
if (S[i] != T[i])
return S[i] - T[i];
return 0;
}
Status Concat(SString T,SString S1, SString S2)
{
int i;
if (S1[0] + S2[0] <= MAXSIZE)
{
//未截断
for (i = 1; i <= S1[0]; i++)
T[i] = S1[i];
for (i = 1; i <= S2[0]; i++)
T[S1[0] + i] = S2[i];
T[0] = S1[0] + S2[0];
}
else//截断
{
printf("截断S2\n");
for (i = 1; i <= S1[0]; i++)
T[i] = S1[i];
for (i = 1; i <= MAXSIZE - S1[0]; i++)
T[S1[0] + i] = S2[i];
T[0] = MAXSIZE;
}
return OK;
}
Status SubString(SString Sub, SString S, int pos, int len)
{//用Sub返回串的第pos个字符起长度为len的子串
int i;
if (pos<1 || pos>S[0] || len<0 || len>S[0] - pos + 1)
{printf("pos或len有误\n"); return 0;}
for (i = 1; i <= len; i++)
Sub[i] = S[pos + i - 1];
Sub[0] = len;
return OK;
}
int Index(SString S, SString T, int pos)
{//返回子串T在主串S中第pos个字符之后的位置。若不存在, 则函数返回值为0

int i = pos;// i用于主串S中当前位置下标值，若pos不为1，则从pos位置开始匹配
int j = 1;// j用于子串T中当前位置下标值
while (i <= S[0] && j <= T[0])
{
if (S[i] == T[j])
{//两字母相等则继续
i++; j++;
}
else
{
i = i - j + 1+1;// i退回到上次匹配首位的下一位
//i-j+1回到0位，因为0位为长度，移到下标为1处
j = 1;
}
}
if (j > T[0])//j现在等于T[0]+1
return (i - T[0]);//i-(T[0]+1)+1,移到下标1处
else return 0;

}
void Outline(SString S)
{
int i;
for (i = 1; i <= S[0]; i++)
printf("%c", S[i]);
printf("\n");
}
int main()
{
int cord;
SString S, chars,s1,s2,T;
do
{
printf("\n\n1.StrAssign 生成串\n");
printf("2.StrLength 求串长\n");
printf("3.StrCompare 串比较\n");
printf("4.Concat 串连接\n");
printf("5.输出串\n");
printf("6.SubString 求子串\n");
printf("7.Index 模式匹配\n");
scanf("%d", &cord);
switch (cord)
{
case 1:
{
printf("输入要生成的串\n");
scanf("%s", chars);
if (StrAssign(S, chars))
printf("成功\n");
}break;
case 2:
{
printf("串长为%d", StrLength(S));
}break;
case 3:
{
int i;
printf("输入要比较的串：\n");
scanf("%s", chars);
i = StrCompare(S, chars);
if (i > 0)printf("串S>串chars\n");
else if (i < 0)printf("串S<串chars\n");
else printf("串S=串chars\n");
}break;
case 4:
{
printf("输入要连接的串S1：\n");
scanf("%s", chars);
StrAssign(s1, chars);
printf("输入要连接的串S1：\n");
scanf("%s", chars);
StrAssign(s2, chars);
Concat(T, s1, s2);
printf("连接后的新串为:\n");
Outline(T);
}break;
case 5:Outline(S); break;
case 6:
{
int pos, len;
printf("输入子串的起始位置和子串的长度\n");
scanf("%d %d", &pos, &len);
SubString(T, S, pos, len);
printf("子串为:\n");
Outline(T);
}break;
case 7:
{
int pos;
printf("输入pos \n");
scanf("%d", &pos);
printf("输入子串\n");
scanf("%s", chars);
StrAssign(T, chars);
printf("S的第%d个字母起第一次匹配\n",Index(S, T, pos));
}break;
}
} while (cord<9);

return 0;
}