算术表达式求值演示——严蔚敏版数据结构实习题1

该算法目前还只能计算个位数的四则运算，
如 5-9+8*7/1
二25+9*8/74则不能计算
改进中……

Stack.calss

/**
 * ***********CopyRight**************
 *-------Powered by QianXunNet-----
 *-----Version 1.00   2009-01-17-----
 *-----   Design BY  NiChao    -----
 *^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
 */
package yanweimin.StackOpertor;

public class Stack {
	
	     /*
	      *   将数据num存入栈
	      * @param num 带存入的数据或运算符
	      */
			public void push(int num)
			{
				if(this.p == maxsize)
					System.out.println("栈已满");
				else
				{
					this.p++;
					this.stackvalue[p] = num;
				}
			}
			
			/*
			 * 从栈中取出一个数据或运算符
			 * @return temp   取出的值
			 */
			public int pop()
			{
				int temp = -1;
				        //栈已经空
				if(this.p != -1)
				{
					temp =  this.stackvalue[p];
					this.p--;
				}
				return temp;
			}
			
			/*
			 *  检验是否是运算符
			 *  @param num 待检验的字符
			 *  @ true/false
			 */
			public boolean isOperator(int num)
			{
				if(num == 42 || num == 43 || num ==45 || num ==47)
					return true;
				else 
					return false;
			}
			/*
			 *  对两个数进行计算
			 * @param a  b   两个操作数
			 * @param operator 运算符]
			 * @return jieguo 运算结果
			 */
		   public int twoJieGuo(int a, int operator, int b)
		   {
			   switch(operator)
			   {
			   case 42 : return (a * b);
			   case 43 : return (a + b);
			   case 45 : return (a -b);
			   case 47 : return (a/b);
			   }
			   return 0;
		   }
		   /*
		    * 判断运算符的优先顺序
		    * @ param  operator 带判断的运算符
		    * @ return youxianma
 		    */
		   public int youxianMa(int operator)
		   {
			   switch(operator)
			   {
			   case 42: return 2;
			   case 47: return 2;
			   case 43: return 1;
			   case 45: return 1;
			   }
			   return 0;
		   }
	
	     //栈的最大容量
 int maxsize =20;
        //栈数组
    int[] stackvalue =  new int[maxsize];
       // 栈内的指针  孔栈的时候为-1
 int p = -1;
}

YunSuanFu.java

/**
 * ***********CopyRight**************
 *-------Powered by QianXunNet-----
 *-----Version 1.00   2009-01-17-----
 *-----   Design BY  NiChao    -----
 *^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
 */

package yanweimin.StackOpertor;

import yanweimin.StackOpertor.Stack;
import java.util.Scanner;
public class YunSuanFu {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
                      //定义变量
		Stack yunsuanfu = new Stack();       //运算符栈
		Stack shu = new Stack();                 //操作数栈
		 String ex = "";   //带运算的表达式
		 int zhizhen =0;       //字符串上指示的指针
		 int operator = 0;   //操作符
		 int operated1=0,operated2 = 0;   //操作数
		 
		 Scanner cin = new Scanner(System.in);
		 System.out.println("input a biaodashi:");
		 ex = cin.nextLine();
		 		while(true)
		 		{
		 			//判断是否为运算符
		 			if(yunsuanfu.isOperator(  (int) ex.charAt(zhizhen) ) )
		 			{
		 				         //需要进行运算符的比较
		 				if(yunsuanfu.p != -1)
		 				{
		 					               //先运算栈内的
		 					if(yunsuanfu.youxianMa( (int) ex.charAt(zhizhen) ) <= yunsuanfu.youxianMa((int) yunsuanfu.stackvalue[yunsuanfu.p] ))
		 							{
		 						         operated1 = shu.pop();
		 						         operated2 = shu.pop();
		 						         operator = yunsuanfu.pop();
		 						        shu.push(  shu.twoJieGuo(operated2, operator,operated1)  );
		 							}
		 				}
		 				yunsuanfu.push((int)  ex.charAt(zhizhen) );
		 					
		 			}
		 			          //为运算数时
		 			else
		 			{                   
		 				 shu.push((int) (ex.charAt(zhizhen)-48));		 					 
		 			}
		 			zhizhen++;
		 			if(zhizhen >=ex.length())
		 				 break;
		 		}
		 		  //将剩余运算
		 			while(yunsuanfu.p != -1)
		 			{
		 				operated1 = shu.pop();
		 				operated2 = shu.pop();
		 				operator = yunsuanfu.pop();
		 				shu.push( shu.twoJieGuo(operated2,operator,operated1));
		 			}
		 			//取出表达式的最终结果
		 			
		 			int last = shu.pop();
		 			System.out.print("你输入的表达式："+ex+"=");
		 			System.out.println(last);
		
	}

}