KMP

来源：互联网发布：数控铣削编程加图案编辑：程序博客网时间：2024/06/07 05:37

今天有兴致学习了一下kmp算法，这里复杂度从普通匹配的O(m*n) 变成了O(m+n)#include <iostream>#include <cstdio>#include <cstring>using namespace std;//先找到模式字符串的next函数，若p[k]=p[j]，即p[next[j]]=p[j]，那么：p[1]p[2]…p[k-1]p[k]= p[j-k+1]p[j-k+2]…p[j-1]p[j] void GetNext(char* t,int* next){int j = 0;int k = -1;next[0] = -1;while(j < strlen(t)){if(k == -1 || t[k] == t[j]){next[j+1] = k+1;j++;k++;}else{k = next[k];//这里递归，知道k=-1； }}}int KMP(char* s,char* t,int pos,int* next){int i = pos;int j = 0;while(s[i] != '\0'){if(j == -1){i++;j++;}//匹配好就结束 if(t[j] == '\0'){return (i-j+1);}if(s[i] == t[j]){i++;j++;}else{j = next[j];}}}int main(){int next[10001];char a[100] = "123456789123456";char b[100] = "789123";GetNext(b,next);int n = KMP(a,b,0,next);printf("%d\n",n);//cout<<KMP(a,b,0,next)<<endl;return 0;}

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