1.kmp
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
void get_nextval(char *str,int *nextval)
{
int i,j;
i = 0;
j = -1;
nextval[0] = -1;
int len = strlen(str);
while(i < len)
{
if(j==-1 || str[j]==str[i])//str[i]表示后缀的单个字符，str[j]表示前缀的单个字符
{
++i;
++j;
if(str[i] != str[j]) //若当前字符与前缀字符不同，则当前的j为nextvale在i位置的值
{
nextval[i] = j;
}
else //否则将前缀字符的nextval值赋给后缀字符的nextval
{
nextval[i] = nextval[j];
}
}
else
{
j = nextval[j];//若字符不同，则j值回溯
}
}
}
void get_next(char *str,int *next)
{
int i,j;
i = 0;
j = -1;
next[0] = -1;
int len = strlen(str);
while(i < len)
{
if(j==-1 || str[i]==str[j])
{
++i;
++j;
next[i] = j;
}
else
{
j = next[j];
}
}
}
int Index_KMP(char *strF,char *strS,int pos)
{
int i = pos;
int j = 0;//字串中当前位置下标值
int next[255];
get_nextval(strS,next);
int lenF = strlen(strF);
int lenS = strlen(strS);
while(i < lenF && j < lenS) //若i小于lenF且j小于lenS,循环继续
{
if(j == -1 || strF[i]==strS[j])//两字符相等或者j为-1则继续
{
++i;
++j;
}
else
{
j = next[j];//j回退合适的位置，i不变
}
}
if(j >= lenS)return i-lenS;//必须要由j使循环退出才说明找到了这个子串的位置
else return 0;
}
int main()
{
char *strF = "abcdecdefg";
char *strS = "defg";
printf("%d
",Index_KMP(strF,strS,0));
return 0;
}x
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void get_nextval(char *str,int *nextval)9
{10
int i,j;11
i = 0;12
j = -1;13
nextval[0] = -1;14
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int len = strlen(str);17
while(i < len) 18
{19
if(j==-1 || str[j]==str[i])//str[i]表示后缀的单个字符，str[j]表示前缀的单个字符20
{21
++i;22
++j;23
if(str[i] != str[j]) //若当前字符与前缀字符不同，则当前的j为nextvale在i位置的值24
{25
nextval[i] = j;26
}27
else //否则将前缀字符的nextval值赋给后缀字符的nextval28
{29
nextval[i] = nextval[j];30
}31
}32
else33
{34
j = nextval[j];//若字符不同，则j值回溯35
}36
}37
}38
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void get_next(char *str,int *next)41
{42
int i,j;43
i = 0;44
j = -1;45
next[0] = -1;46
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int len = strlen(str);48
while(i < len)49
{50
if(j==-1 || str[i]==str[j])51
{52
++i;53
++j;54
next[i] = j;55
}56
else57
{58
j = next[j];59
}60
}61
}62
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int Index_KMP(char *strF,char *strS,int pos)66
{67
int i = pos;68
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int j = 0;//字串中当前位置下标值70
int next[255];71
get_nextval(strS,next);72
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int lenF = strlen(strF);74
int lenS = strlen(strS);75
while(i < lenF && j < lenS) //若i小于lenF且j小于lenS,循环继续76
{77
if(j == -1 || strF[i]==strS[j])//两字符相等或者j为-1则继续78
{79
++i;80
++j;81
}82
else83
{84
j = next[j];//j回退合适的位置，i不变85
}86
}87
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if(j >= lenS)return i-lenS;//必须要由j使循环退出才说明找到了这个子串的位置89
else return 0;90
}91
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int main()95
{96
char *strF = "abcdecdefg";97
char *strS = "defg";98
printf("%d
",Index_KMP(strF,strS,0));99
return 0;100
}