今天來解YKL31(UVA10268)：498'

498'

計算多項式的微分
並把x代進去，求多項式全部的和

就像下圖題目解釋的

coef=>a
n-i=>n
pow(x, n - i - 1)=>X的n次方

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;


int derivative(int x, const vector<int>& coef) {
    int n = coef.size() - 1;  
    int result = 0;
    
    for (int i = 0; i < n; i++) {
        result += coef[i] * (n - i) * pow(x, n - i - 1);  
    }
    
    return result;
}

int main() {
    int x;
    while (cin >> x) {
        vector<int> coef;
        int c;
        
        while (cin >> c) {
            coef.push_back(c);
            if (cin.peek() == '\n' || cin.peek() == EOF) break;  
        }   
        cout << derivative(x, coef) << endl;

    }
    
    return 0;
}