expr.cpp

设计一个算法

#include<iostream.h>
#include<string.h>
#include<stdlib.h>
#include<memory.h>
#include<fstream.h>
#include<iomanip.h>
char st[101];
long tmp,stack[40001],p;
long calculator(long num1,long num2,char symbol)
{
	switch(symbol)
	{
		case '+':return num1+num2;
		case '-':return num1-num2;
		case '*':return num1*num2;
		case '/':return num1/num2;
		case '%':return num1%num2;
	}
	return 0;
}
int main()
{
	p=0;
	memset(stack,0,sizeof(stack));
	ifstream input("input.txt");
	ofstream output("output.txt");
	while(input>>st)
	{
		if (!strcmp(st,"+") || !strcmp(st,"-") || !strcmp(st,"*") || !strcmp(st,"/") || !strcmp(st,"%")) 
		{
			tmp=calculator(stack[p-1],stack[p],st[0]);
			stack[p]=0;
			p--;
			stack[p]=tmp;                     //pop_stack
		}
		else stack[++p]=atoi(st);       //push_stack
	}
	output<<stack[1]<<endl;
	return 0;
}