BZOJ 4393: [Usaco2015 Dec]Fruit Feast

DP

#include<cstdio>
using namespace std;
int T,A,B,F[5000005],G[5000005];
int main(){
	scanf("%d%d%d",&T,&A,&B);
	F[0]=1;
	for (int i=0; i<=T; i++) F[i+A]|=F[i],F[i+B]|=F[i];
	for (int i=0; i<=T; i++) G[i/2]|=F[i];
	for (int i=0; i<=T; i++) G[i+A]|=G[i],G[i+B]|=G[i];
	for (int i=T; i>=0; i--)
		if (F[i] || G[i]){
			printf("%d\n",i);
			return 0;
		}
	return 0;
}