C++實現KMP演算法

標籤：

#include <iostream>#include <stdlib.h>#include <vector>using namespace std;void NEXT(const string &T, vector<int> &next){//按模式串產生vector,next(T.size())next[0] = -1;for(int i = 1; i < T.size(); i++){int j = next[i - 1];while(T[i] != T[j + 1] && j >= 0)j = next[j];//遞推計算if(T[i] == T[j + 1])next[i] = j + 1;elsenext[i] = 0;}}string::size_type COUNT_KMP(const string &S, const string &T){//利用模式串T的next函數求T在主串S中的個數count的KMP演算法//其中T非空，vector<int>next(T.size());NEXT(T, next);string::size_type index, count=0;for(index=0; index < S.size(); ++index){int pos=0;string::size_type iter = index;while(pos < T.size() && iter<S.size()){if(S[iter] == T[pos]){++iter;++pos;}else{if(pos == 0)++iter;elsepos = next[pos - 1] + 1;}}if(pos == T.size() && (iter - index) == T.size())++count;}return count;}int main(){string S, T;cout<<"請輸入主串（參照的）"<<endl;cin>>S;cout<<"請輸入子串（要尋找的）"<<endl;cin>>T;string::size_type count =COUNT_KMP(S,T);cout<<"一共有 "<<count<<" 個子串"<<endl;return 0;}

C++實現KMP演算法