九度OJ——1019简单计算器

#include <iostream>
#include <cstdio>
#include <stack>
#include <vector>
#include <cstdlib>
using namespace std;

string str;
vector<string> latter,mid;
stack<string> s;
stack<double> caculate;

//栈外优先级
int icp(char ch)
{
    int result = 0;
    if(ch == '#'){
        result = 0;
    }
    if(ch == '*'||ch == '/'){
        result = 4;
    }
    if(ch == '+'||ch == '-'){
        result = 2;
    }   
    return result;      
 } 

//栈内优先级
int isp(char ch)
{
    int result = 0;
    if(ch == '#'){
        result = 0;
    }
    if(ch == '*'||ch == '/'){
        result = 5;
    }
    if(ch == '+'||ch == '-'){
        result = 3;
    }   
    return result;      
 } 

//生成中缀表达式
void Median()
{
    for(int i = 0 ; i < str.length() ; i++){
        if(str[i] >= '0' && str[i] <= '9'){
            int j;
            for(j = i ; j < str.length() ; j++){
                if(str[j]>= '0' && str[j] <= '9'){
                    continue;
                }else{
                    break;
                }
            }
            mid.push_back(string(str,i,j-i));
            i = j-1;
        }else if(str[i] == ' '){
            continue;
        }else{
            mid.push_back(str.substr(i,1));
        }
    }
    mid.push_back(string(1,'#'));
}

//生成后缀表达式
void Latter()
{
    s.push(string(1,'#'));
    for(int i = 0 ; i < mid.size() ; i++){
        //是数字直接追加大后缀表达式 
        if(mid[i][0] >= '0' && mid[i][0] <= '9'){
            latter.push_back(mid[i]);
        }else{//是运算符
            //栈顶元素的优先级小于栈外元素的优先级，栈外元素入栈 
            string ch = s.top();
            if(isp(ch[0]) < icp(mid[i][0])){
                s.push(string(mid[i]));
            }else if(isp(ch[0]) > icp(mid[i][0])){
                //栈顶元素的优先级大于栈外元素的优先级，栈顶元素出栈到后缀表达式 
                latter.push_back(ch);
                s.pop();
                i--;
            }else{//栈顶元素的优先级到等于栈外元素的优先级 ，说明遍历到"#",结束 
                s.pop();
            }
        }
    } 
 } 

int main()
{
    while(1){
        mid.clear();
        latter.clear();
        str.clear();
        getline(cin,str);
        if(str[0] == '0'){
            break;
        }
        Median();
        Latter();
        for(int i = 0 ; i < latter.size() ; i++){
            if(latter[i][0] >= '0' && latter[i][0] <= '9'){
                double num = atof(latter[i].c_str());
                caculate.push(num);
            }else{
                double b = caculate.top();
                caculate.pop();
                double a = caculate.top();
                caculate.pop();
                double c;
                switch(latter[i][0]){
                    case '+': c = a + b;break;
                    case '-': c = a - b;break;
                    case '*': c = a * b;break;
                    case '/': c = a / b;break;
                }
                caculate.push(c);
            }
        }
        double result = caculate.top();
        caculate.pop();
        printf("%.2f\n",result);
    }

    return 0; 
}