原理

• 規則：

遍歷字串

1. 對於數字：直接進棧
2. 對於符號：
    （1）從棧中彈出右運算元
    （2）從棧中彈出左運算元
    （3）根據符號進行運算
    （4）將運算結果壓棧

遍歷結束：棧中唯一的數字作為計算結果

例子：

輸入：831-5*+         相當於求：8+（3-1）*5
輸出：18

程式碼

stack.h

#ifndef __STACK_H
#define __STACK_H

#define MAX_SIZE 1024



typedef struct STACK
{
	void* Stack_Sqe[
 
MAX_SIZE];
	int size;				
}Stack;



Stack* Init_Stack(void);

void Push_Stack(Stack* stack, void* data);
void Pop_Stack(Stack* stack);

void* Top_Stack(Stack* stack);

void Clear_Stack(Stack* stack);
void Free_Stack(Stack* stack);

int Size_Stack(Stack* stack);


#endif

stack.c

#include "../include/stack.h"
 

#include <stdlib.h>


Stack* Init_Stack(void)
{
	Stack* stack = (Stack*)malloc(sizeof(Stack));
	stack->size =0;		
				
	for(int i=0; i<MAX_SIZE; i++)
	{
		stack->Stack_Sqe[i]=NULL;				
	}
	return stack;		
}


void Push_Stack(Stack* stack, void* data)
{
	if(stack == NULL) return;
	if(data ==
 
 NULL) return;
	stack->Stack_Sqe[stack->size++] = data;			
}



void Pop_Stack(Stack* stack)
{
	if(stack == NULL) return;
	if(stack->size==0) return;
	stack->Stack_Sqe[stack->size-1]=NULL;
	stack->size--;		
}


void* Top_Stack(Stack* stack)
{
	if(stack == NULL)return NULL;
	return stack->Stack_Sqe[stack->size-1];			
}



void Clear_Stack(Stack* stack)
{
	if(stack == NULL)return;
	for(int i=0; i<stack->size; i++)
	{
			stack->Stack_Sqe[i]=NULL;				
	}		
}




void Free_Stack(Stack* stack)
{
	if(stack == NULL)
	    return;
	free(stack);			
}



int Size_Stack(Stack* stack)
{
	return stack->size;		
}

mian.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "../include/stack.h"




int CalculateSuffix(char* str)
{

	Stack* stack = Init_Stack();
	int tmp[64]={0};

	int len = strlen(str);
	for(int i=0; i<len; i++)
	{
		if(str[i]>47 && str[i]<58)//數字
		{
			tmp[i]= (int)(str[i]-48);
			Push_Stack(stack,&tmp[i]);
		}
		else
		{
			switch(str[i])
			{
				case '-':
					{
						int* c1 = Top_Stack(stack);
						int cc1 = *c1;
						int right1 = cc1;
						Pop_Stack(stack);

						int* d1 = Top_Stack(stack);
						int dd1 = *d1;
						int left1 = dd1;
						Pop_Stack(stack);

						int res1 = left1-right1;
						Push_Stack(stack,&res1);
						break;

					}
				case '+':
					{
						int* c2 = Top_Stack(stack);
						int cc2 = *c2;
						int right2 = cc2;
						Pop_Stack(stack);

						int* d2 = Top_Stack(stack);
						int dd2 = *d2;
						int left2 = dd2;
						Pop_Stack(stack);

						int res2 = left2+right2;
						Push_Stack(stack,&res2);
						break;
					}
					
				case '*':
					{
						int* c3 = Top_Stack(stack);
						int cc3 = *c3;
						int right3 = cc3;
						Pop_Stack(stack);

						int* d3 = Top_Stack(stack);
						int dd3 = *d3;
						int left3 = dd3;
						Pop_Stack(stack);

						int res3 = left3*right3;
						Push_Stack(stack,&res3);
						break;
					}

				case '/':
					{
						int* c4 = Top_Stack(stack);
						int cc4 = *c4;
						int right4 = cc4;
						Pop_Stack(stack);

						int* d4 = Top_Stack(stack);
						int dd4 = *d4;
						int left4 = dd4;
						Pop_Stack(stack);

						int res4 = left4/right4;
						Push_Stack(stack,&res4);
						break;

					}	
				default:
					printf("error ");
					break;
					
			}
		}

	}


	int* result = Top_Stack(stack);
	return *result;

}

int main(void)
{

	char str[64]={0};
	int result=0;
	printf("input:");
	scanf("%s",str);

	result =CalculateSuffix(str);
    printf("output:");
	printf("%d\n",result);
									
									
	return 0;
									
}

結果：