LightOJ 1341

唯一分解定理后的思维题
给我搞成了dfs,但是能过
比较坑的地方是n = i * i这种是不算的
也就是刚好平方根*平方根那种不计入答案，到现在仍然不知道为啥

const int maxn = 1e6 + 10;
int prime[maxn], cnt = 0;
bool isprime[maxn];

void getprime() {
	cnt = 0;
	for (int i = 2; i < maxn; ++i) {
		if (!isprime[i])	prime[cnt++] = i;
		for (int j = 0; j < cnt && i * prime[j] < maxn; ++j) {
			isprime[i * prime[j]] = 1;
			if (i % prime[j] == 0)	break;
		}
	}
}

int n, k, ans, cas = 1;
int limit, sqr;
int num[44] = { 0 }, tot = 0;
int cass[44] = { 0 }, to[44];
void dfs(int now, int id, int flag) {
	if (now > sqr)	return;
	if (now >= k && flag) {
		ans++;
		//printf("%lld\n", now);
	}
	if (id > limit)	return;
	int mul = 1;
	for (int i = 0; i <= cass[id]; ++i) {
		dfs(now * mul, id + 1, i);
		mul *= to[id];
	}
}

void solve() {
	tot = 1;
	n = rd(); k = rd();
	sqr = sqrt(n);
	if (sqr * sqr == n)	sqr--;
	if (k * k > n) {
		printf("Case %lld: 0\n", cas++);
		return;
	}
	int tmp = n;
	for (int i = 0; i < cnt; ++i) {
		while (tmp % prime[i] == 0) {
			if (tmp == 1)	break;
			num[tot++] = prime[i];
			tmp /= prime[i];
		}
		if (tmp == 1)	break;
	}
	if (tmp != 1)	num[tot++] = tmp;

	limit = 0;
	for (int i = 1; i < tot; ++i) {
		if (num[i] == num[i - 1])	cass[limit] ++;
		else cass[++limit] = 1, to[limit] = num[i];
	}

	ans = 0;
	dfs(1, 1, 1);
	printf("Case %lld: %lld\n", cas++, ans);
}

void solve2() {
	n = rd(); k = rd();
	if (k * k > n) {
		printf("Case %lld: 0\n", cas++);
		return;
	}
	int tmp = n;
	int res = 1;
	for (int i = 0; i < cnt; ++i) {
		int ans = 0;
		while (tmp % prime[i] == 0) {
			if (tmp == 1)	break;
			num[tot++] = prime[i];
			tmp /= prime[i];
			ans++;
		}
		if (ans)	res *= (1 + ans);
		if (tmp == 1)	break;
	}
	if (tmp == 1)	res /= 2;

	for (ll i = 1; i < k; ++i) if (n % i == 0)	res--;
	printf("Case %lld: %lld\n", cas++, res);
}

signed main() {
	//test();
	getprime();
	int t = 1;
	t = rd();
	while (t--)	solve();
	return 0;
}

标签：tmp,prime,int,1341,LightOJ,++,ans,lld
来源： https://www.cnblogs.com/wanshe-li/p/14117867.html