KMP模式匹配算法实现-简单例子

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class StringMatch extends JFrame {

   TextField tf1;//文本框1，大字符串
   TextField tf2;//文本框2，指定匹配的字符串
   TextField tf3;//文本框3，输入从第几个字符开始匹配
   JButton jb;//按钮
   JLabel lab1,lab2,lab3,lab4,lab5;//标签
   JPanel panel1,panel2,panel3;//面板
   String str,s;//大字符串，指定需要匹配的字符串
   int pos;//开始匹配的起始位置
StringMatch(){
   //初始化组件

   tf1=new TextField(10);
   tf2=new TextField(5);
   tf3=new TextField(3);
   lab1=new JLabel("请输入一串英文字符（不超过10个字符）");
   lab2=new JLabel("请输入一串英文字符（不超过5个字符）");
   //返回匹配结果
       lab3=new JLabel("单击按钮，输出是否匹配以及匹配的字符串下标");
       lab5=new JLabel("输入开始匹配的起始位置");
       //按钮
   jb=new JButton();
   jb.setPreferredSize(new Dimension(100, 25));
   // seticon(jb);
   jb.setText("确定");

   lab4=new JLabel("结果是：");
   FlowLayout fl=new FlowLayout(FlowLayout.LEFT,10,10);
   GridLayout gr=new GridLayout(3,1);




   //面板1
   panel1=new JPanel();
   panel1.add(lab1);
   panel1.add(tf1);
   panel1.setLayout(gr);
   add(panel1);//水平间距，垂直间距

   //面板2
   panel2=new JPanel();
   panel2.add(lab2);
   panel2.add(tf2);
   panel2.add(lab5);
   panel2.add(tf3);
   panel2.setLayout(gr);
   add(panel2);

   //面板3
   panel3=new JPanel();
   panel3.add(lab3);
   panel3.add(jb);
   panel3.add(lab4);
   panel3.setLayout(fl);
   add(panel3);

   //监听按钮事件
   jb.addActionListener(new ActionListener(){
       public void actionPerformed(ActionEvent e){
           if(tf1.getText().length()==0 || tf2.getText().length()==0 || tf3.getText().length()==0)
               JOptionPane.showMessageDialog(null,"需输入字符！","警告",JOptionPane.WARNING_MESSAGE);
           else
           Match(e);
       }
   });



}
//给按钮设置合适的图片
public void seticon(JButton jb){
   ImageIcon ic=new ImageIcon("D:\\eclipse-java-neon-3-win32-x86_64\\eclipse\\workspace\\Java-exercise\\src\\q-4.jpg");
   Image temp=ic.getImage().getScaledInstance(80,50,ic.getImage().SCALE_DEFAULT);
ic=new ImageIcon(temp);
   jb.setIcon(ic);
}

public void Match(ActionEvent e){
   str=tf1.getText();
   s=tf2.getText();
   pos=Integer.parseInt(tf3.getText());
   if(e.getActionCommand().equals("确定")){
       //返回匹配结果

       lab4.setText("结果是："+String.valueOf(Index_KMP(str,s,pos)));

   }

}
//匹配算法
public int Index_KMP(String S,String T,int pos){
   int lenS=S.length();
   int lenT=T.length();
   int i=pos;
   int j=0;
   int[] next=new int[255];
   //字符串转换成字符数组
   char[] Str=S.toCharArray();
   char[] Ttr=T.toCharArray();
   next=get_nextval(T,next);
   //循环
   while(i<lenS && j<lenT){
       if((j==-1) || Str[i]==Ttr[j]){
           ++i;
           ++j;
       }else
       {
           j=next[j];
       }
   }
   if(j==lenT)
       return i-lenT;
   else
   return -1;
}

//匹配算法的next数组改进
public int[] get_nextval(String T,int[] nextval){
   int i,j;
   int lenT=T.length();
   char[] Ttr=T.toCharArray();
   i=0;
   j=-1;
   nextval[0]=-1;
   while(i<lenT-1){
       if(j==-1 || Ttr[i]==Ttr[j] ){
           ++i;
           ++j;
           if(Ttr[i]!=Ttr[j])nextval[i]=j;
           else
               nextval[i]=nextval[j];
       }
       else
           j=nextval[j];
   }
   return nextval;
}

public static void main(String[] args){
   StringMatch sm=new StringMatch();
   sm.setBounds(300,300,400,250);
   sm.setResizable(false);
       sm.setVisible(true);
       sm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       GridLayout grid=new GridLayout(3,3);
       sm.setLayout(grid);
}
}

运行结果：

KMP模式匹配算法实现-简单例子

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