逆波兰数Java实现

定义^ 自增

* 乘法

+ 加法

栈长度16 超过 上溢出 返回-2  若栈中没有足够的整数供运算 则返回-1 否则返回栈顶

package ali0426;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.Stack;

public class Main {

    public static void main(String[] args) {

        ArrayList<Integer> inputs = new ArrayList<Integer>();
        Scanner in = new Scanner(System.in);
        String line = in.nextLine();
        if(line != null && !line.isEmpty()) {
            int res = resolve(line.trim());
            System.out.println(String.valueOf(res));
        }
    }

    // write your code here
    public static int resolve(String expr) {
    	String str [] = expr.split(" ");
    	
    	
    	Stack<Integer> sta = new Stack<>();
    	int temp1,temp2;
    	//char [] ch = expr.toCharArray();
    	for(int i=0;i<str.length;i++){
    		String  c = str[i];
    		if(sta.size()>16) return -2;  //上溢出
    		if(c.equals("^")){
    			if(sta.size()==0) return -1;
    			else{
    				temp1 = sta.pop();
    				temp1++;
    				sta.push(temp1);
    			}
    				
    			
    		}
    		else if(c.equals("+")){
    			if(sta.size()<2) return -1;
    			else{
    				temp1 =sta.pop();
    				temp2 = sta.pop();
    				sta.push(temp1+temp2);
    			}
    			
    		}
    		else if(c.equals("*")){
    			if(sta.size()<2) return -1;
    			else{
    				temp1 =sta.pop();
    				temp2 =sta.pop();
    				sta.push(temp1*temp2);
    		        
    			}
    			
    		}
    		else if(c.equals(" ")) continue;//处理空格
    		else{
    			sta.add(Integer.parseInt(c));
    		}
    		
    	}
		return sta.peek();

        
       
    }
}