PAT乙级1056 组合数的和 (15 分)

https://pintia.cn/problem-sets/994805260223102976/problems/994805271455449088
暴力解

#include <iostream>
using namespace std;
int main(){
	int sum = 0, N, num[10] = {0};
	cin >> N; 
	for(int i = 0; i < N; ++i)
		cin >> num[i];
	for(int i = 0; i < N; ++i){
		for(int j = 0; j < N; ++j){
			if(j == i)
				continue;
			sum += 10*num[i]+ num[j];
		}
	}
	cout << sum;
	return 0;
} 

找规律

#include <iostream>
int main() {
    int N, sum = 0, temp;
    scanf("%d", &N);
    for (int i = 0; i < N; i++) {
        scanf("%d", &temp);
        sum += temp * 10 * (N - 1) + temp * (N - 1);
    }
    printf("%d", sum);
    return 0;
}