[Project Euler] Problem 20

n! means n (n 1) ... 3 2 1

Find the sum of the digits in the number 100!

这道题的做法和那个求2的1000次方的各位和的思路一样

我们只需要在那道题程序的基础上稍加改变就可以了

#include <iostream>
usingnamespace std;

int main(){
    int sum[200]={1};
    int tmp;
    int all=0;
    for(int i=1;i<=100;i++){
        int carry =0;
        for(int j=0;j<200;j++){
            tmp = sum[j]*i;
            sum[j] = (tmp+carry)%10;
            carry = (tmp+carry)/10;
        }
    }
    for(int j=0;j<200;j++){
        all += sum[j];
    }
    cout << all << endl;
    return0;
}