Divisibility by Eight

cf306c_.cc

int solve(int p, int num){
	if(p==n) printf("%d\n", num);

	if(dp[p][num]!=-1) return dp[p][num]; //this line must go first!	
	//if(p==n && num==0) return dp[n][0] = 0; //ignore empty case, but this over write the correct value
	if(p==n) return dp[p][num%8] = (num%8==0);
	int t = (num*10)+(s[p]-'0');
	//take digit at position p or not
	return dp[p][num%8] = max(solve(p+1, t%8), solve(p+1, num));  
}