Help about the Stack infix operation

[andy8521]

Hello

I have been trying too long for this but I think I am gonna ask for help.

#include<iostream>
#include<string>
#include<math.h>
#include "numStack.h"
#include"charStack.h"

using namespace std;

int getNum(int num[],int count);

int addition(int n1,int n2);
int subtraction(int n1, int n2);
int multiplication(int n1,int n2);
int division(int n1, int n2);

int main(){
		
	string str;
	int stackSize = 0;
	 
	cout<<"Please enter infix line: ";
	getline(cin,str);

	stackSize = str.length();
	int num[50]={0};
	int pushNum = 0;
	
	int popNum1 = 0;
	int popNum2 = 0;
	char popChar = NULL;
	int popResult = 0;
	int j=0;
	
	numStack intStack(stackSize);
	charStack opStack(stackSize);

	for(int i=0;i<stackSize;i++){
		
		
		if(str[i] >= '0' && str[i] <= '9' ){
				
				num[j] = (str[i]-'0');		
				j=j+1;
				
		}
	
		else if(str[i] == '+' || str[i] == '-' ||
			  str[i] == '*' || str[i] == '/' ){
				pushNum = getNum(num,j);
				if((intStack.peek())!=pushNum || pushNum <= 0 ){
					intStack.push(pushNum);
					j=0;
				}
				opStack.push(str[i]);
				
		}
		else if(str[i] == ')'){
				pushNum = getNum(num,j);
				if((intStack.peek())!=pushNum || pushNum<=0 ){
					intStack.push(pushNum);
					j=0;
				}
				else ;
					
					intStack.pop(popNum1);
					intStack.pop(popNum2);
					opStack.pop(popChar);
				       if(popChar == '+'){intStack.push(addition(popNum1,popNum2));}
						else if(popChar == '-'){intStack.push(subtraction(popNum1,popNum2));}
						else if(popChar == '*'){intStack.push(multiplication(popNum1,popNum2));}
						else {intStack.push(division(popNum1,popNum2));}
					
					
			
		}
		else;
		
	}
	intStack.pop(popResult);
	cout<<popResult<<endl;
	return 0;
}

int getNum(int num[],int count){
	
	int calNum = 0;
	int l = 0;	

	for( int k = count -1  ; k >= 0  ; k--){
		calNum = calNum + (num[l] * int(pow(10.0,(k))));
		l = l+1;
	}

	return calNum;
}

int addition(int n1,int n2){return (n1+n2);}
int subtraction(int n1, int n2){return (n2-n1);}
int multiplication(int n1,int n2){return (n1*n2);}
int division(int n1, int n2){return int(n2/n1);}

I am using two stacks to print the output. I know my stacks are working perfectly fine but my output is not as I am expecting. Can someone help me?

infix expression is : (7+(((5*4)-(9-3))*1))
Answer should be : 21