Submission #334263

#	Time	Username	Problem	Language	Result	Execution time	Memory
334263		ChrisT	Snake Escaping (JOI18_snake_escaping)	C++17	75 / 100	2093 ms	40548 KiB

snake_escaping

#include <bits/stdc++.h>
using namespace std;
int val[1 << 20], sum1[1 << 20], sum2[1 << 20]; 
char str[25];
int main() { //nut
	int n,q;
	scanf ("%d %d",&n,&q);
	for (int i = 0; i < (1 << n); i++) {
		char ch; scanf (" %c",&ch); 
		sum2[((1 << n) - 1) ^ i] = sum1[i] = val[i] = ch - '0';
	}
	for (int i = 0; i < n; i++) {
		for (int mask = 0; mask < (1 << n); mask++) if (mask >> i & 1) {
			sum1[mask] += sum1[mask ^ (1 << i)];
			sum2[mask] += sum2[mask ^ (1 << i)];
		}
	}
	while (q--) {
		scanf ("%s",str);
		reverse(str,str+n);
		int cnt0 = 0, cnt1 = 0, cntq = 0;
		for (int i = 0; i < n; i++) {
			if (str[i] == '0') ++cnt0;
			else if (str[i] == '1') ++cnt1;
			else ++cntq;
		}
		if (cntq <= cnt0 && cntq <= cnt1) { //brute force ?s
			vector<int> pos; pos.reserve(cntq);
			int mask = 0, ret = 0;
			for (int i = 0; i < n; i++) {
				if (str[i] == '?') pos.push_back(i);
				mask |= (str[i] == '1') << i;
			}
			for (int qmask = 0; qmask < (1 << cntq); qmask++) {
				int nmask = mask;
				for (int i = 0; i < cntq; i++) nmask |= (qmask >> i & 1) << pos[i];
				ret += val[nmask];
			}
			printf ("%d\n",ret);
		} else if (cnt0 <= cnt1) { //PIE
			vector<int> pos; pos.reserve(cnt0);
			int mask = 0, ret = 0;
			for (int i = 0; i < n; i++) {
				if (str[i] == '0') pos.push_back(i);
				mask |= (str[i] != '1') << i;
			}
			for (int mask0 = 0; mask0 < (1 << cnt0); mask0++) {
				int nmask = mask;
				for (int i = 0; i < cnt0; i++) nmask ^= (mask0 >> i & 1) << pos[i];
				ret += (__builtin_popcount(mask0) & 1 ? -1 : 1) * sum2[nmask];
			}
			printf ("%d\n",ret);
		} else { //'' ''
			vector<int> pos; pos.reserve(cnt1);
			int mask = 0, ret = 0;
			for (int i = 0; i < n; i++) {
				if (str[i] == '1') pos.push_back(i);
				mask |= (str[i] != '0') << i;
			}
			for (int mask1 = 0; mask1 < (1 << cnt1); mask1++) {
				int nmask = mask;
				for (int i = 0; i < cnt1; i++) nmask ^= (mask1 >> i & 1) << pos[i];
				ret += (__builtin_popcount(mask1) & 1 ? -1 : 1) * sum1[nmask];
			}
			printf ("%d\n",ret);
		}
	}
    return 0;
}

Compilation message (stderr)

snake_escaping.cpp: In function 'int main()':
snake_escaping.cpp:7:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf ("%d %d",&n,&q);
      |  ~~~~~~^~~~~~~~~~~~~~~
snake_escaping.cpp:9:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    9 |   char ch; scanf (" %c",&ch);
      |            ~~~~~~^~~~~~~~~~~
snake_escaping.cpp:19:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   19 |   scanf ("%s",str);
      |   ~~~~~~^~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 10 / 10
• Subtask 4: 53 / 53
• Subtask 5: 0 / 25