#include<iostream>
using namespace std;
int ans,curCnt;
int curNumber;
int cnt;
void work(int k,int cur){//k<=cnt-1,cur<=curNumber
	if(k==cnt-1){
		if(curNumber>=cur&&curNumber<=cur+9)curCnt++;// ÕâÒ»¾äshit!!!
	}
	else{
		if(cur+(cnt-k)*9<curNumber)return;
		int i;
		for(i=0;i<10;i++){
			if(cur+i>curNumber)return;
			work(k+1,cur+i);
		}
	}
}

int main(){
	int n;
	cin>>n;
	if(n&1){
		cout<<0<<endl;
		return 0;
	}
	ans=2;
	int i;
	cnt=n/2;
	for(i=1;i<cnt*9;i++){
		curNumber=i;
		curCnt=0;//0,max
		work(0,0);
		ans+=(curCnt*curCnt);
	}
	cout<<ans<<endl;
	return 0;
}

• Re:brute force (686) ysjjovo 2011-03-13 21:40:12
  • Re:brute force (511) ysjjovo 2011-03-13 21:43:14
    • Re:brute force (577) ysjjovo 2011-03-13 21:44:22
      • Re:brute force (32) ysjjovo 2011-03-13 21:45:01
• 容斥原理 (628) ysjjovo 2011-03-14 13:13:06