kmp字符串匹配算法

#include<iostream>#include<string>using namespace std;//定义KMP算法系统class KMP_Sys{private: //主串 string P_data; //模式串 string S_data; //next值的整型指针 int *next; //nextval值的整型指针 int *nextval; //模式串在主串,0为不存在 int pos; //KMP核心算法 void KMP_Index(int *next) { int i = 1; int j = 1; while(i <= int(P_data.size() - 1) && j <= int(S_data.size()) - 1) { //继续比较后继字符 if(j == 0 || P_data[i] == S_data[j]) { ++i; ++j; } //模式串向右移动 else j = next[j]; } //匹配成功 if (j > int(S_data.size()) - 1) pos = i - int(S_data.size()) + 1; //匹配不成功 else pos = 0; }public: //初始化KMP系统 KMP_Sys() { //因为字符串从1位置开始匹配,所以0位置赋值为空格 P_data = " "; S_data = " "; //next与nextval均为长度256的数组 next = new int[256]; nextval = new int[256]; } ~KMP_Sys() { //回收动态申请空间 delete next; delete nextval; } //求模式串的next值 void GetNext() { int i = 1; next[1] = 0; int j = 0; while(i < int(S_data.size()) - 1) { if(j == 0 || S_data[i] == S_data[j]) { ++i; ++j; next[i] = j; } else j = next[j]; } } //求模式串的nextval值 void GetNextval() { int i = 1; nextval[1] = 0; int j = 0; while(i < int(S_data.size()) - 1) { if(j == 0 || S_data[i] == S_data[j]) { ++i; ++j; if(S_data[i] != S_data[j]) nextval[i] = j; else nextval[i] = nextval[j]; } else j = nextval[j]; } } //KMP系统的运行实体 void run() { cout << "主串:"; string s1, s2; getline(cin, s1); P_data = P_data + s1; cout << "模式串:"; getline(cin, s2); S_data = S_data + s2; //模式串输入后分别求它的next与nextval值 GetNext(); GetNextval(); cout << "next值:"; //输出next值 for(int i = 1; i <= int(S_data.size()) - 1; i++) cout << next[i]; cout << endl; //输出nextval值 cout << "nextval值:"; for(int i = 1; i <= int(S_data.size()) - 1; i++) cout << nextval[i]; cout << endl; KMP_Index(next); cout << "位置:" << pos << endl; }};void main(){ KMP_Sys kmp; //运行KMP系统 kmp.run();}