Submission #219488

#	Time	Username	Problem	Language	Result	Execution time	Memory
219488		Sorting	Linear Garden (IOI08_linear_garden)	C++14	2 / 100	1597 ms	1436 KiB

linear_garden

#include <bits/stdc++.h>

using namespace std;

const int kN = 1e6 + 3;

int n, m;
string garden;

int dp[kN][1 << 5][5];
bool illegal[1 << 5];
int new_idx_mask[1 << 4];

int get_count(int pos, int mask, int diff){
	if(diff < 0 || diff > 4)
		return 0;
	mask |= 1 << diff;
	if(illegal[mask])
		return 0;
	if(pos == n)
		return 1;

	int &ans = dp[pos][new_idx_mask[mask]][diff];
	ans = 0;

	ans += get_count(pos + 1, mask, diff + 1);
	ans += get_count(pos + 1, mask, diff - 1);
	ans = (ans >= m) ? (ans - m) : ans;

	return ans;
}

int get_count_solved(int pos, int mask, int diff){
	if(diff < 0 || diff > 4)
		return 0;
	mask |= 1 << diff;
	if(illegal[mask])
		return 0;
	if(pos == n)
		return 1;

	return dp[pos][new_idx_mask[mask]][diff];
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);

	cin >> n >> m >> garden;

	for(int i = 1; i < (1 << 5); ++i){
		int min_bit, max_bit;
		for(int j = 0; j < 5; ++j){
			if((1 << j) & i){
				min_bit = j;
				break;
			}
		}
		for(int j = 4; j >= 0; --j){
			if((1 << j) & i){
				max_bit = j;
				break;
			}
		}

		if(max_bit - min_bit > 2){
			illegal[i] = true;
		}
	}

	new_idx_mask[0] = 0;
	for(int i = 1; i < (1 << 5); ++i){
		if(illegal[i])
			new_idx_mask[i] = new_idx_mask[i - 1];
		else
			new_idx_mask[i] = new_idx_mask[i - 1] + 1;
	}

	for(int pos = n - 1; pos >= 1; --pos){
		for(int mask = 0; mask < 32; ++mask){
			for(int diff = 0; diff < 5; ++diff){
				get_count(pos, mask, diff);
			}
		}
	}

	int ans = 1;
	int mask = (1 << 2), diff = 2;
	for(int i = 0; i < n; ++i){
		if(garden[i] == 'P'){
			ans += get_count_solved(i + 1, mask, diff - 1);
			ans = (ans >= m) ? (ans - m) : ans;
		}
		if(garden[i] == 'L'){
			mask |= 1 << (diff - 1);
			diff -= 1;
		}
		else{
			mask |= 1 << (diff + 1);
			diff += 1;
		}
	}

	cout << ans << "\n";
}

Compilation message (stderr)

In function 'int main()':
cc1plus: warning: iteration 15 invokes undefined behavior [-Waggressive-loop-optimizations]
linear_garden.cpp:72:19: note: within this loop
  for(int i = 1; i < (1 << 5); ++i){
                 ~~^~~~~~~~~~
linear_garden.cpp:66:14: warning: 'max_bit' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if(max_bit - min_bit > 2){
      ~~~~~~~~^~~~~~~~~
linear_garden.cpp:66:14: warning: 'min_bit' may be used uninitialized in this function [-Wmaybe-uninitialized]

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