串的模式匹配算法（BF、KMP）

#include<stdio.h>
#define MAXSIZE 100
typedef struct {
int str[MAXSIZE];
int length;
}seqstring;


seqstring *buildstring()
{
seqstring *t;
int i = 0;
char ch;
t = (seqstring *)malloc(sizeof(seqstring));
int k;
while ((ch = getchar()) != '\n')
{
t->str[i] = ch;
++i;
}
t->length = i;
t->str[i] = '\0';
return t;
}


void display(seqstring s)
{
int i = 0;
for (; i<s.length; i++)
printf("%5c", s.str[i]);
putchar('\n');
}


void getnext(seqstring p,int next[])
{
int i = 0, j = -1;
next[0] = -1;
while (i < p.length)
{
if (j == -1 || p.str[i] == p.str[j])
{
++i;
++j;
next[i] = j;
}
else
j = next[j];
}
}


int kmp(seqstring t, seqstring p, int next[])//t爲主串，p爲模式串
{
int i = 0, j = 0;
while (i < t.length&&j < p.length)
{
if (j == -1 || t.str[i] == p.str[j])
{
i++;
j++;
}
else
j = next[j];
}
if (j == p.length)
return (i - p.length+1);
else
return -1;
}


int bf(seqstring p, seqstring t)
{
int i = 0, succ = 0,j;
while ((i <= p.length - t.length) && (!succ))//主串上的循環i
{
succ = 1;//控制succ爲關鍵
j = 0;
while ((j < t.length) && succ)//模式串的循環j
{
if (p.str[i + j] == t.str[j])
j++;
else
succ = 0;
}
++i;
if (succ)
return i;//返回首次匹配成功主串的起始位置
}
return -1;
}


void main()
{
seqstring *s;
s = buildstring();
display(*s);
seqstring *t;
t = buildstring();
display(*t);
int next[MAXSIZE];
getnext(*t, next);
printf("模式匹配kmp：%d\n", kmp(*s, *t, next));
printf("模式匹配bf：%d\n", bf(*s, *t));
}