package code;

import java.util.Stack;

public class Code227 {
	
 public int calculate(String s) {
 	Stack<Integer> numSck=new Stack<Integer>();
 	Stack<Character> opSck=new Stack<Character>();
 	int i=0;
 	s=s.replace(" ", "");
 	int len=s.length();
 	int result=0;
 	while(i<len){
 		char c=s.charAt(i);
 		//nums
 		if(c>='0' && c<='9'){
 			int x=0;
 			while(i<len && s.charAt(i)>='0' && s.charAt(i)<='9'){
 				x*=10;
 				x+=s.charAt(i)-'0';
 				i++;
 			}
 			numSck.push(x);
 		}
 		//运算符
 		else{
 			if(c=='*' || c=='/'){
					while(!opSck.isEmpty() && (opSck.peek()=='*' || opSck.peek()=='/')){
						int a=numSck.pop();
						int b=numSck.pop();
						char op=opSck.pop();
						if(op=='*')
							b*=a;
						else
							b/=a;
						numSck.push(b);
					}
 			}
 			else{
 				while(!opSck.isEmpty()){
 					int a=numSck.pop();
 					int b=numSck.pop();
 					char op=opSck.pop();
 					if(op=='*')
 						b*=a;
 					else if(op=='/')
 						b/=a;
 					else if(op=='+')
 						b+=a;
 					else 
 						b-=a;
 					numSck.push(b);
 				}
 			}
 			opSck.push(c);
 			i++;
 		}
 		//如果处理完所有的字符,则对栈内运算
 		if(i==len){
				while(!opSck.isEmpty()){
					int a=numSck.pop();
					int b=numSck.pop();
					char op=opSck.pop();
					if(op=='*')
						b*=a;
					else if(op=='/')
						b/=a;
					else if(op=='+')
						b+=a;
					else 
						b-=a;
					numSck.push(b);
				}
				if(!numSck.isEmpty())
					result=numSck.pop();
				else 
					result=0;
 		}
 	}
 return result;
 }
 public static void main(String[] args){
 	System.out.println(new Code227().calculate("1-1+1"));
 }
}