P1149 火柴棒等式

#include <bits/stdc++.h>
using namespace std;
const int num[] = {6, 2, 5, 5, 4, 5, 6, 3, 7, 6};
int dp[2000];
int solve(int k) {
	if(dp[k]) return dp[k];
	if(k < 10) return dp[k] = num[k];
	else if(k<100){
		int a = k/10;
		int b = k%10;
		return dp[k] = num[a] + num[b];
	}
	else {
		int a = k/100;
		int b = k%10;
		int c = k/10%10;
		return dp[k] = num[a] + num[b] + num[c];
	}
}
int main() {
	memset(dp, 0, sizeof(dp));
	int n;
	cin >> n;
	n-=4;
	int cnt = 0;
	for(int i = 0; i <= 999; i++) {
		for(int j = 0; j <= 999; j++) {
			int k = i + j;
			if(n == solve(k) + solve(i) + solve(j)) cnt++;
		}
	}
	cout << cnt;
}