火柴棒等式题解

#include <bits/stdc++.h>
using namespace std;
int a[2001] = {6},c[10] = {6,2,5,5,4,5,6,3,7,6},x,y,n;
int main(void){
    cin >> n;
    for(int i = 1;i <= 2000;i ++){
        x = i;
        while(x){
            a[i] = a[i] + c[x % 10];
            x /= 10;
        }
    }
    y = 0;
    for(int i = 0;i <= 1000;i ++){
        for(int j = 0;j <= 1000;j ++){
        	if(a[i] + a[j] + a[i + j] + 4 == n) y++;
		}
    }
    cout << y << endl;
    return 0;
}