node.java

来自「Binary Expression Tree」· Java 代码 · 共 65 行

//
// Group 5
//
import java.lang.*;
import java.util.*;
public class Node {
    static final int NUMBER = 0, OPERATOR = 1;   // values for kind.                                      
    int kind;       // type of node.
    double number;  // The value in a node.
    char op;        // The operator in a node.
    Node left;		// left node.
    Node right;		// right node.
    
    Node(double val) {
		// Constructor for making a node of type NUMBER.
       kind = NUMBER;
       number = val;
    }
    
    Node(char val) {
       kind = OPERATOR;
       this.op = val;
    }    

    Node(Node left, char op, Node right) {
		// Constructor for making a node of type OPERATOR.

       kind = OPERATOR;
       this.op = op;
       this.left = left;
       this.right = right;
    }
	// Return the value of the expression.
	static double getValue( Node node ) {
	     if ( node.kind == NUMBER) {
	        return node.number;
	     }
	     else { 
	        double leftVal = getValue( node.left );
	        double rightVal = getValue( node.right );
	        switch(node.op) {
	           case '+':  return leftVal + rightVal;
	           case '-':  return leftVal - rightVal;
	           case '*':  return leftVal * rightVal;
	           case '/':  return leftVal / rightVal;
	           default:   return Double.NaN;  // return Not a Number.
	        }
	     }
	  }

public static void main (String[] args){
		Node t5 = new Node(4);
		Node t6 = new Node(9);
		Node t7 = new Node(5);
		Node t8 = new Node(3);
		Node t9 = new Node(4);
		Node t4 = new Node(t8, '*', t9);
		Node t2 = new Node(t4, '+', t5);
		Node t3 = new Node(t6, '-', t7);
		Node t1 = new Node(t2, '/', t3);
		double value = getValue(t1); // get Value.
		System.out.println("Result = " + value); // show value.
	}
}