高中生程式解題: f640: 函數運算式求值－資工趴趴熊的小天地

Content

有三個函數：

f(x) = 2x – 3
g(x, y) = 2x +y – 7
h(x, y, z) = 3x – 2y + z

另有一個由這三個函數所組成的運算式，依序給你其中的函數名稱及參數，請求出這個運算式的值。例如：

h f 5 g 3 4 3

代表

h(f(5), g(3, 4), 3)
=h(7, 3, 3)
=18

python:

from sys import stdin
def f(x):
    return eval(f'2*{x}-3')
def g(x,y):
    return eval(f'2*{x}+{y}-7')
def h(x,y,z):
    return eval(f'3*{x}-2*{y}+{z}')

s=stdin.readline().strip().split()
p=[i for i ,c in enumerate(s) if c in "fgh"]
a=[]
while len(s)!=0:
    a1=s[-1]
    a.append(s.pop())
    if a1=='f':
        f1=a.pop()
        f2=a.pop()
        a.append(f(f2))
    if a1=='g':
        g1=a.pop()
        g2=a.pop()
        g3=a.pop()
        a.append(g(g2,g3))
    if a1=='h':
        h1=a.pop()
        h2=a.pop()
        h3=a.pop()
        h4=a.pop()
        a.append(h(h2,h3,h4))
print(*a)

C++

#include <iostream>
#include <string>
using namespace std;
 
int eval() {
    string s;
    cin>>s;
    if(s[0]=='f'){
    	int x=eval();
    	return 2*x-3;
	}
	else if(s[0]=='g'){
        int x=eval();
        int y=eval();
        return 2 * x + y - 7;
    }
    else if (s[0]=='h')
    {
        int x=eval();
        int y=eval();
        int z=eval();
        return 3 * x - 2 * y + z;
    }
    else{
        return stoi(s); //str to int
    }
    
    return 0;
}

int main(){
    cout<<eval()<<'\n';
}

C++

#include <iostream>
#include <string>
#include <stack>
using namespace std;

int main(){
    string s;
    stack<string> stk1;
    stack<int> stk2;

    while (cin>>s)
    {
        stk1.push(s);
    }
    while (!stk1.empty())
    {
        s = stk1.top();
        stk1.pop();
        if(s=="f"){ //都要用雙引號，因為推出來給s的是string
            int x = stk2.top(); stk2.pop();
            stk2.push(2*x-3);
        }
        else if(s=="g")
        {
            int x = stk2.top(); stk2.pop();
            int y = stk2.top(); stk2.pop();
            stk2.push(2*x+y-7);
        }
        else if (s=="h")
        {
            int x = stk2.top(); stk2.pop();
            int y = stk2.top(); stk2.pop();
            int z = stk2.top(); stk2.pop();
            stk2.push(3*x-2*y+z);
        }
        else
        {
            stk2.push(stoi(s));
        }
    }
    cout<<stk2.top()<<'\n';
    
    return 0;
}