# Example of KMP algorithm

• 2020-05-26 09:50:18
• OfStack

Example of KMP algorithm

KMP algorithm is a pattern matching algorithm jointly proposed by Knuth, Morris and Pratt. For any pattern and target sequence, KMP algorithm can complete matching search in linear time without degradation. It is a very excellent pattern matching algorithm.

Analysis: the key of KMP is to find the value of next, preprocess the value of next first, and then scan it once. The complexity is O (m+n).

Example code:

``````
#include<stdio.h>
#include<string.h>
#define N 1000005
int s[N];
int p[N];
int next[N];
int m,n;
void getnext(){
int j=0,k=-1;
next[0]=-1;
while(j<m){
if(k==-1||p[j]==p[k]){
j++;
k++;
next[j]=k;
}
else
k=next[k];
}
}
int kmp(){
int i=0,j=0;
getnext();
while(i<n){
if(j==-1||s[i]==p[j]){
i++;
j++;
}
else
j=next[j];
if(j==m)
return i;
}
return -1;
}
int main(){
int t;
scanf("%d",&t);
while(t--){
scanf("%d%d",&n,&m);
for(int i=0;i<n;i++)
scanf("%d",&s[i]);
for(int i=0;i<m;i++)
scanf("%d",&p[i]);
if(kmp()==-1)
printf("-1\n");
else
printf("%d\n",kmp()-m+1);
}
return 0;
}
``````

The above is the example of KMP algorithm on the data structure and algorithm of the site there are a lot of articles, I hope you search, thank you for reading, hope to help you, thank you for the support of the site!

Related articles: