C :

#include<stdio.h>
#include<math.h>
#include<malloc.h>
typedef struct Node
{
	char data;
	int da;
	struct Node *next;
}Node;
typedef struct Lstack
{
	struct Node *top;
}Lstack;
int Init(Lstack *s)
{
	if(!s)
		return 0;
	else
	{
	   s->top=NULL;
	   return 1;
	}
}
int Empty(Lstack s)
{
	return !s.top;
}
int Push1(Lstack *s,int e)
{
	Node *newn=(Node*)malloc(sizeof(Node));
	if(!newn)
		return 0;
	else
	{
		newn->da=e;
		newn->next=s->top;
		s->top=newn;
		return 1;
	}
}
int Push2(Lstack *s,char e)
{
	Node *newn=(Node*)malloc(sizeof(Node));
	if(!newn)
		return 0;
	else
	{
		newn->data=e;
		newn->next=s->top;
		s->top=newn;
		return 1;
	}
}
int Pop1(Lstack *s,int *e)
{
	if(Empty(*s))
		return 0;
	else
	{
		Node *p=s->top;
		*e=p->da;
		s->top=p->next;
		free(p);
		return 1;
	}
}
int Pop2(Lstack *s,char *e)
{
	if(Empty(*s))
		return 0;
	else
	{
		Node *p=s->top;
		*e=p->data;
		s->top=p->next;
		free(p);
		return 1;
	}
}
int Get(Lstack s,char *e)
{
	if(Empty(s))
		return 0;
	else
	{
		*e=s.top->data;
		return 1;
	}
}
void main()
{
	Lstack sta,ch;
	Init(&sta);
	Init(&ch);
	char e,op;
	char b[100];
	char c[100];
	int a[100];
	int i,j,k,r,legth;
	int x,y,sum;
	while(gets(b)!=NULL)
	{
		i=0;
		for(j=0;b[j]!='\0';i++)
		{
			
			
			   for(r=0;b[j]>='0'&&b[j]<='9'&&b[j]!='\0';j++)
			       r++;
			   a[i]=0;
			   for(k=0;k<r;k++)
			   {
				   a[i]=a[i]+(b[j-1-k]-48)*pow(10,k);
			   }
			   if(b[j]!='\0')
			   {
			    c[i]=b[j];
				j++;
			   }
			
		}
		legth=i-1;
		Push1(&sta,a[0]);
		Push2(&ch,c[0]);
		Push1(&sta,a[1]);
		for(i=1;i<legth;i++)
		{
			if(c[i]=='*'||c[i]=='/')
			{
				Get(ch,&e);
				if(e=='+'||e=='-')
				{
					Push2(&ch,c[i]);
			        Push1(&sta,a[i+1]);
			        Pop1(&sta,&x);
				    Pop1(&sta,&y);
				    Pop2(&ch,&op);
				       
			        switch(op)
					{
		        	case'*':sum=y*x;break;
			        case'/':sum=y/x;break;
		        	case'+':sum=y+x;break;
		        	case'-':sum=y-x;break;
		        	default:break;
					}
			        Push1(&sta,sum);
				}
				else if(e=='*'||e=='/')
				{
					Pop1(&sta,&x);
				    Pop1(&sta,&y);
				    Pop2(&ch,&op);
			        switch(op)
					{
		        	case'*':sum=y*x;break;
			        case'/':sum=y/x;break;
		        	case'+':sum=y+x;break;
		        	case'-':sum=y-x;break;
		        	default:break;
					} 
					Push1(&sta,sum);
					Push2(&ch,c[i]);
					Push1(&sta,a[i+1]);

				}
			}
			else if(c[i]=='+'||c[i]=='-')
			{ 	   
				    Pop1(&sta,&x);
				    Pop1(&sta,&y);
				    Pop2(&ch,&op);
			        switch(op)
					{
		        	case'*':sum=y*x;break;
			        case'/':sum=y/x;break;
		        	case'+':sum=y+x;break;
		        	case'-':sum=y-x;break;
		        	default:break;
					} 
					Push1(&sta,sum);
					Push2(&ch,c[i]);
					Push1(&sta,a[i+1]);

			}
		}
		            Pop1(&sta,&x);
				    Pop1(&sta,&y);
				    Pop2(&ch,&op);
			        switch(op)
					{
		        	case'*':sum=y*x;break;
			        case'/':sum=y/x;break;
		        	case'+':sum=y+x;break;
		        	case'-':sum=y-x;break;
		        	default:break;
					}
					Push1(&sta,sum);
		           printf("%d\n",sum);
	}
}
			

C++ :

#include<stdio.h>
#include<ctype.h>
#include<assert.h>

char str[1024];
int a[1024];
int c;
int n;

int getnum() {
	int ret=0;
	while(isdigit(str[c])) {
		ret=ret*10+str[c]-'0';
		c++;
	}
	return ret;
}

int main() {
	int i,j,s;
	while(gets(str)) {
		c=0,s=1;
		if (str[c]=='-') c++,s=-1;
		for(j=0;;) {
			int t=getnum();
			while(str[c]=='*' || str[c]=='/') {
				char op=str[c];
				c++;
				int t1=getnum();
				if (op=='*') {
					t*=t1;
				} else {
					assert(t1!=0);
					assert(t%t1==0);
					t/=t1;
				}
			}
			a[j++]=s*t;
			if (str[c]=='-') s=-1;
			else if (str[c]=='+') s=1;
			else break;
			c++;
		}
		s=0;
		for(i=0;i<j;i++) {
			s+=a[i];
			assert(s<1000000000 && s>=-1000000000);
		}
		printf("%d\n",s);
	}
	return 0;
}

Java :

import java.io.*;
import java.util.Stack;
public class Main 
{
	public static Boolean gogo(char a,char b)
	{
		if(a=='*'||a=='/'||b=='+'||b=='-')
			return true;
		else
			return false;
	}
	public static void main(String[] args) throws IOException 
	{
		BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));
		String s;
		char t;
		int a,b;
		Stack<Character> p=new Stack<Character>();
		Stack<Integer> d=new Stack<Integer>();
		while((s=cin.readLine())!=null) //cin.ready()
		{
			for(int i=0;i<s.length();i++)
			{
				t=s.charAt(i);
				if(t=='+'||t=='-'||t=='*'||t=='/')
				{
					while(p.empty()!=true)
					{
						if(gogo(p.peek(),t))
						{
							b=d.pop();
							a=d.pop();
							if(p.peek()=='+')
							{
								a=a+b;
							}
							else if(p.peek()=='-')
							{
								a=a-b;
							}
							else if(p.peek()=='*')
							{
								a=a*b;
							}
							else if(p.peek()=='/')
							{
								a=a/b;
							}
							d.push(a);
							p.pop();
						}
						else
							break;
					}
					p.push(t);
				}
				else
				{
					a=t-'0';
					for(int j=i+1;j<s.length();j++)
					{
						if(Character.isDigit(s.charAt(j)))
						{
							a=a*10+(s.charAt(j)-'0');
							i++;
						}
						else
						{
							i=j-1;
							break;
						}
					}
					d.push(a);
				}
			}
			while(p.empty()!=true)
			{
				b=d.pop();
				a=d.pop();
				if(p.peek()=='+')
				{
					a=a+b;
				}
				else if(p.peek()=='-')
				{
					a=a-b;
				}
				else if(p.peek()=='*')
				{
					a=a*b;
				}
				else if(p.peek()=='/')
				{
					a=a/b;
				}
				d.push(a);
				p.pop();
			}
			System.out.println(d.peek());
			p.clear();
			d.clear();
		}
		cin.close();
	}
}

Python :

# coding=utf-8
from sys import argv

if __name__ == "__main__":
    while True:
        try:
            exp = input()
        except:
            break
        print(int(eval(exp)))