//支持帶括號的表達式,支持+-*/、^(指數(shù))、取負、!(階乘)
#include <iostream>
#include <stack>
#include <math.h>

using namespace std;

double inStack(); ? //核心函數(shù)，將操作符有序的入棧計算， 最后返回結(jié)果
void calculate(stack<char>& Ope, stack<double>& Num); ?//用來計算加減乘除, 結(jié)果放在數(shù)字棧頂
void factorial(stack<double>& Num); ? //用來計算階乘
int priority(char ope_); ? //用來計算操作符的優(yōu)先級

int main() {
?? ?double result; ? //最后的結(jié)果

?? ?cout << "請輸入：\n";
?? ?result = inStack(); ? //將緩沖區(qū)的操作符和數(shù)字壓入棧?

?? ?cout << "結(jié)果是：\n" << result;

?? ?return 0;
}

double inStack() {
?? ?stack<char> Ope;
?? ?stack<double> Num;
?? ?char ope_;
?? ?double num_;

?? ?while (1) {
?? ??? ?if (cin.peek() >= '0' && cin.peek() <= '9') { ?//判斷下一個是否是數(shù)字
?? ??? ??? ?cin >> num_;
?? ??? ??? ?Num.push(num_); ? //數(shù)字直接入棧
?? ??? ?}
?? ??? ?else {
?? ??? ??? ?cin >> ope_;
?? ??? ??? ?if (ope_ == '=') {
?? ??? ??? ??? ?while (!Ope.empty()) calculate(Ope, Num); //如果符號棧不空，就一直計算
?? ??? ??? ??? ?return Num.top(); ?//如果是等號且符號棧頂為空，就返回數(shù)字棧頂元素
?? ??? ??? ?}
?? ??? ??? ?else if (ope_ == '!') factorial(Num); ?//如果是！就階乘
?? ??? ??? ?else if (ope_ == '(' ||Ope.empty()) Ope.push(ope_); ? ?//如果符號是左括號或符號棧為空直接壓入
?? ??? ??? ?else if (ope_ == ')') { ?//如果是右括號
?? ??? ??? ??? ?while (Ope.top() != '(') calculate(Ope, Num); //一直計算完括號里的
?? ??? ??? ??? ?Ope.pop(); ?//左括號出棧
?? ??? ??? ?}
?? ??? ??? ?else if (priority(Ope.top()) >= priority(ope_)) { ?//如果棧頂符號的優(yōu)先級大于等于當(dāng)前
?? ??? ??? ??? ?calculate(Ope, Num); ? //計算結(jié)果壓入數(shù)字棧,取出當(dāng)前棧頂
?? ??? ??? ??? ?Ope.push(ope_); ?//壓入當(dāng)前符號
?? ??? ??? ?}
?? ??? ??? ?else Ope.push(ope_); ?//否則就壓入符號棧
?? ??? ?}
?? ?}
}

void calculate(stack<char>& Ope, stack<double>& Num) {
?? ?double a, b;

?? ?if (Ope.top() == '-') {
?? ??? ?a = Num.top(); Num.pop();
?? ??? ?Ope.pop(); ? //取出負號
?? ??? ?Num.push(-a); ?//壓入負值
?? ??? ?if (!Num.empty()) {
?? ??? ??? ?if(Ope.empty() || Ope.top() != '(')
?? ??? ??? ??? ?Ope.push('+'); ?//如果前面還有數(shù)字，就壓入+，即變成加負值
?? ??? ?}
?? ?}
?? ?else {
?? ??? ?a = Num.top(); Num.pop();
?? ??? ?b = Num.top(); Num.pop();

?? ??? ?if (Ope.top() == '+') Num.push(b + a);
?? ??? ?else if (Ope.top() == '*') Num.push(b * a);
?? ??? ?else if (Ope.top() == '/') Num.push(b / a);
?? ??? ?else if (Ope.top() == '^') Num.push(pow(b, a));

?? ??? ?Ope.pop();
?? ?}
}

void factorial(stack<double>& Num) {
?? ?int a = static_cast<int>(Num.top());
?? ?int result=1;

?? ?for (int i = 1; i <= a; i++) result *= i;

?? ?Num.push(static_cast<double>(result));
}

int priority(char ope_) {
?? ?if (ope_ == '(') return 0;
?? ?else if (ope_ == '+' || ope_ == '-') return 1;
?? ?else if (ope_ == '*' || ope_ == '/') return 2;
?? ?else if (ope_ == '^') return 3;
}