编辑代码

#include <iostream>
#include <stack>     //栈的库函数
#include <string>    //字符串库函数
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
using namespace std;

//1.判断括号是否匹配
bool ArePair(char opening,char closing){
    if(opening == '(' && closing == ')' || 
       opening == '[' && closing == ']' || 
       opening == '{' && closing == '}' ){
           return true;
       }
    return false;
}
bool ParenthesisMatched(string expression){
    stack<char> S;        //定义一个栈用于存放括号
    for(int i = 0;i < expression.length();i++){
        if(expression[i]  == '(' || expression[i]  == '[' || expression[i]  == '{'){
            S.push(expression[i]);
        }
        else if(expression[i] == ')' || expression[i] == ']' || expression[i] == '}' ){
            if(S.empty() || !ArePair(S.top(),expression[i])){
                return false;
            }    
            S.pop();
        }
    }
    if(!S.empty()){
        return false;
    }
    return true;
}

//2.中缀表达式转后缀表达式
//(1)判断是否为操作数
bool IsOperand(char C){
    if(C >= '0' && C <= '9' ||
       C >= 'a' && C <= 'z' || 
       C >= 'A' && C <= 'Z'){
           return true;
       }
    return false;
}
//(2)判断是否为操作符
bool IsOperator(char C){
    if(C == '+' || C == '-' || C == '*' || C == '/' || C == '^'){
        return true;
    }
    return false;
}
//(3)确定操作符的优先级
int GetOperatorWeight(char operator0){
    int weight = -1;
    switch(operator0){
        case '+':
        case '-':
            weight = 1;
            break;
        case '*':
        case '/':
        case '^':
            weight = 2;
            break;
    }
    return weight;
}
//(4)比较当前操作符合栈顶操作符的优先级
bool HeightPrecedence(char operator1,char operator2){
    int op1Weight = GetOperatorWeight(operator1);
	int op2Weight = GetOperatorWeight(operator2);
    if(op1Weight > op2Weight){
        return true;
    }
    return false;
}
//(5)中缀表达式转后缀表达式
string Transform(string infix){
    string postfix = "";
    stack<char> S;
    for(int i = 0;i < infix.length();i++){
        if(infix[i] == ' ' || infix[i] == ',')continue;
        else if(infix[i]  == '(' || infix[i]  == '[' || infix[i]  == '{'){
            S.push(infix[i]);
        }
        else if(infix[i]  == ')' || infix[i]  == ']' || infix[i]  == '}'){
            while(!ArePair(S.top(),infix[i])){
                postfix += S.top();
                S.pop();
            }
            S.pop();
        }
        else if(IsOperand(infix[i])){
            postfix += infix[i];
        }
        else if(IsOperator(infix[i])){
            if(S.empty() || S.top()  == '(' || S.top()  == '[' || S.top()  == '{'){
                S.push(infix[i]);
            }
            else if(HeightPrecedence(infix[i],S.top())){
                S.push(infix[i]);
            }else{
                postfix += S.top();
                S.pop();
                S.push(infix[i]);
            }
        }
    }
    while(!S.empty()){
        postfix += S.top();
        S.pop();
    }
    return postfix;
}

//3.后缀表达式计算
int Calculate(string expression) {
    stack<char> S;
    char c1 = ' ';
    char c2 = ' ';
    char c3 = ' ';
    int num1 = 0;
    int num2 = 0;
    int result = 0;
    for (int i = 0; i < expression.length(); i++) {
        if (IsOperand(expression[i])) {
            S.push(expression[i]);
        }
        else {
            c2 = S.top();
            //printf("%c", c1);
            num2 = atoi(&c2);
            S.pop();
            c1 = S.top();
            //printf("%c", c2);
            num1 = atoi(&c1);
            S.pop();
            if (expression[i] == '*') {
                result = num1 * num2;
            }
            else if (expression[i] == '/') {
                result = num1 / num2;
            }
            else if (expression[i] == '^') {
                result = pow(num1, num2);
            }
            else if (expression[i] == '+') {
                result = num1 + num2;
            }
            else if (expression[i] == '-') {
                result = num1 - num2;
            }
            
            S.push(result + '0');
        }
    }
    c3 = S.top();
    result = atoi(&c3);
    S.pop();
    return result;
}

int main() {
    //(1)定义字符串接收内容
    //char str[1024];
    //printf("请输入一个简单的二元算数表达式:");
    //scanf("%s",str);
    //printf("\n%s",str);

    //char *str = "([5 + 9) - 2 * 3]";
    //string expression(str);

    string expression = "9 - 5 * (3 - 2)";
    int result = 0;
    //printf("%s",expression.c_str());

    //判断表达式括号是否匹配
    if(ParenthesisMatched(expression)){
        expression = Transform(expression);
        printf("后缀表达式为: %s",expression.c_str());
        result = Calculate(expression);
        printf("\nresult = %d",result);
    }else{
        printf("表达式括号不匹配,请检查后重新输入!");
        return 0;
    }
}