java数据结构与算法之中缀表达式转为后缀表达式的方法

本文实例讲述了java数据结构与算法之中缀表达式转为后缀表达式的方法。分享给大家供大家参考，具体如下：

//stack
public class stackx {
  private int top;
  private char[] stackarray;
  private int maxsize;
  //constructor
  public stackx(int maxsize){
    this.maxsize = maxsize;
    this.top = -1;
    stackarray = new char[this.maxsize];
  }
  //put item on top of stack
  public void push(char push){
    stackarray[++top] = push;
  }
  //take item from top of stack
  public char pop(){
    return stackarray[top--];
  }
  //peek the top item from stack
  public char peek(){
    return stackarray[top];
  }
  //peek the character at index n
  public char peekn(int index){
    return stackarray[index];
  }
  //true if stack is empty
  public boolean isempty(){
    return (top == -1);
  }
  //return stack size
  public int size(){
    return top+1;
  }
}
//intopost
public class intopost {
  private stackx mystack;
  private string input;
  private string output="";
  //constructor
  public intopost(string input){
    this.input = input;
    mystack = new stackx(this.input.length());
  }
  //do translation to postfix
  public string dotrans(){
    for(int i=0; i<input.length(); i++){
      char ch = input.charat(i);
      switch(ch){
      case '+':
      case '-':
        this.getoper(ch,1);
        break;
      case '*':
      case '/':
        this.getoper(ch,2);
        break;
      case '(':
        this.getoper(ch, 3);
        break;
      case ')':
        this.getoper(ch, 4);
        break;
      default:
        this.output = this.output + ch;
      }
    }
    while(!this.mystack.isempty()){
      this.output = this.output + this.mystack.pop();
    }
    return this.output;
  }
  //get operator from input
  public void getoper(char ch, int prect1){
    char temp;
    if(this.mystack.isempty()||prect1==3){
      this.mystack.push(ch);
    }
    else if(prect1==4){
      while(!this.mystack.isempty()){
        temp = this.mystack.pop();
        if(temp=='(')continue;
        this.output = this.output + temp;
      }
    }
    else if(prect1==1){
      temp = this.mystack.peek();
      if(temp=='(') this.mystack.push(ch);
      else{
        this.output = this.output + this.mystack.pop();
        this.mystack.push(ch);
      }
    }
    else{
      temp = this.mystack.peek();
      if(temp=='('||temp=='+'||temp=='-') this.mystack.push(ch);
      else{
        this.output = this.output + this.mystack.pop();
      }
    }
  }
}
//test
public class testintopost {
  private static intopost intopost;
  private static string str;
  public static void main(string []args){
    str = "((a+b)*c)-d";
    intopost = new intopost(str);
    system.out.println(intopost.dotrans());
  }
}

ps:算法实现不是很完善，有些复杂的表达式解析要出错，写出来做个纪念！

更多关于java算法相关内容感兴趣的读者可查看本站专题：《java数据结构与算法教程》、《java操作dom节点技巧总结》、《java文件与目录操作技巧汇总》和《java缓存操作技巧汇总》

希望本文所述对大家java程序设计有所帮助。