c++多位数的浮点数运算中缀表达式求和，可用于多位整型数

例题

求中缀表达式
( 34 - 72.3 ) * 54.7 - 82.4 的值

原理

运用两个栈
stack<char>s;//存放运算符
stack<double>ss;//存放浮点数

话不多说上代码

// c++浮点数的中缀表达式求和
#include<iostream>
#include<fstream>
#include<cmath>
#include<stack>
using namespace std;
int Getpriority(char ch) {//确定优先级 
//+ -：1	
//* /：2		
    if (ch == '+' || ch == '-') {
        return 1;
    }
    else if (ch == '*' || ch == '/') {
        return 2;
    }
}
bool IsOperator(char ch)//判断是否为运算符 
{
    if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
        return true;
    return false;
}
double operations(char t, double left, double right) {//运算 
    double sum;
    switch (t) {
    case '+':
        sum = left + right;
        break;
    case '-':
        sum = left - right;
        break;
    case '*':
        sum = left * right;
        break;
    case '/':
        if (right != 0) {
            sum = left / right;
            break;
        }
        else {
            cout << "error" << endl;
            exit(0);
        }
    }
    return sum;
}
void Infix_summation(char* cur) { //中缀求和 
    stack<char> s;//存放运算符 
    stack<double>ss;//存放浮点数 
    char* c = cur;
    while (*c != '\0') {
        if (*c == ' ') {
            c++;
            continue;
        }
        else if (*c >= '0' && *c <= '9') {
            double t = *c - '0';
            c++;
            while (*c >= '0' && *c <= '9') {
                t = t * 10 + *c - '0';
                c++;
            }
            if (*c == '.') {
                c++;
                int i = 1;
                while (*c >= '0' && *c <= '9') {
                    t = t + pow(0.1, i) * (*c - '0');
                    i++;
                    c++;
                }
            }
            ss.push(t);
        }
        else if (IsOperator(*c)) {
            if (s.empty()) {
                s.push(*c);
                c++;
            }
            else if (Getpriority(*c) > Getpriority(s.top())) {
                s.push(*c);
                c++;
            }
            else if (Getpriority(*c) <= Getpriority(s.top())&&s.top()!='(') {
            loop1:   char t = s.top();
                s.pop();
                double right = ss.top();
                ss.pop();
                double left = ss.top();
                ss.pop();
                double sum;
                sum = operations(t, left, right);
                ss.push(sum);
                if (!s.empty() && Getpriority(*c) <= Getpriority(s.top())&&s.top()!='(') {
                    goto loop1;
                }
                s.push(*c);
                c++;
            }
            else if(s.top()=='('){
            	s.push(*c);
                c++;
			}
    	}
    	else if(*c=='('){
            s.push(*c);
            c++;
		}
        else if (*c == ')') {
        loop2:	if (s.top() != '(') {
            char t = s.top();
            s.pop();
            double right = ss.top();
            ss.pop();
            double left = ss.top();
            ss.pop();
            double sum;
            sum = operations(t, left, right);
            ss.push(sum);
        	}
	        if (!s.empty() && s.top() != '(') {
	            goto loop2;
	        }
	        s.pop();
	        c++;
        }
    }
    while (!s.empty()) {
        char t = s.top();
        s.pop();
        double right = ss.top();
        ss.pop();
        double left = ss.top();
        ss.pop();
        double sum;
        sum = operations(t, left, right);
        ss.push(sum);
    }
    double tmp = ss.top();
    cout << tmp << endl;
}
void Test()
{
    char posture[1000] = "( 34 - 72.3 ) * 54.7 - 82.4 ";
    Infix_summation(posture);
}

int main()
{
    Test();
    return 0;
}

运行结果

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