栈应用 - 后缀表达式的计算

来源：互联网发布：英雄联盟魔兽世界知乎编辑：程序博客网时间：2024/05/22 07:49

有关栈API详情参看我的另一篇博文：栈的链式存储 - API实现

遍历后缀表达式中的数字和符号
对于数字：进栈
对于符号：
从栈中弹出右操作数
从栈中弹出左操作数
根据符号进行运算
将运算结果压入栈中
遍历结束：栈中的唯一数字为计算结果

#include <stdio.h>#include "LinkStack.h"int isNumber3(char c){return ('0' <= c) && (c <= '9');}int isOperator3(char c){return (c == '+') || (c == '-') || (c == '*') || (c == '/');}int value(char c){return (c - '0');}int express(int left, int right, char op){int ret = 0;switch (op){case '+':ret = left + right;break;case '-':ret = left - right;break;case '*':ret = left * right;break;case '/':ret = left / right;break;default:break;}return ret;}int compute(const char* exp){LinkStack* stack = LinkStack_Create();int ret = 0;int i = 0;while (exp[i] != '\0'){if (isNumber3(exp[i])){LinkStack_Push(stack, (void*)value(exp[i]));}else if (isOperator3(exp[i])){int right = (int)LinkStack_Pop(stack);int left = (int)LinkStack_Pop(stack);int result = express(left, right, exp[i]);LinkStack_Push(stack, (void*)result);}else{printf("Invalid expression!");break;}i++;}if ((LinkStack_Size(stack) == 1) && (exp[i] == '\0')){ret = (int)LinkStack_Pop(stack);}else{printf("Invalid expression!");}LinkStack_Destroy(stack);return ret;}int main(){printf("8 + (3 - 1) * 5  = %d\n", compute("831-5*+"));return 0;}

工程文件详情：Github

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