Submission #373190

#	Time	Username	Problem	Language	Result	Execution time	Memory
373190		luciocf	Lamps (JOI19_lamps)	C++14	47 / 100	2 ms	492 KiB

lamp

#include <bits/stdc++.h>
 
using namespace std;
 
const int maxn = 2e3+10;
const int inf = 1e9+10;
 
char a[maxn], b[maxn];

int ate[maxn][2];

int pref[maxn][2];
 
int dp[maxn][2];

struct SegmentTree
{
	int tree[4*maxn];

	void build(int node, int l, int r)
	{
		tree[node] = inf;
		if (l == r) return;

		int mid = (l+r)>>1;

		build(2*node, l, mid); build(2*node+1, mid+1, r);
	}

	void upd(int node, int l, int r, int pos, int v)
	{
		if (l == r)
		{
			tree[node] = v;
			return;
		}

		int mid = (l+r)>>1;

		if (pos <= mid) upd(2*node, l, mid, pos, v);
		else upd(2*node+1, mid+1, r, pos, v);

		tree[node] = min(tree[2*node], tree[2*node+1]);
	}

	int query(int node, int l, int r, int a, int b)
	{
		if (l > r || l > b || r < a) return inf;
		if (l >= a && r <= b) return tree[node];

		int mid = (l+r)>>1;

		return min(query(2*node, l, mid, a, b), query(2*node+1, mid+1, r, a, b));
	}
} seg[2];
 
int main(void)
{
	int n;
	scanf("%d", &n);
 
	for (int i = 1; i <= n; i++)
		scanf(" %c", &a[i]);
 
	for (int i = 1;  i <= n; i++)
		scanf(" %c", &b[i]);
 	
	for (int i = 1; i <= n; i++)
	{
		if (a[i] == '1') ate[i][0] = 0;
		else ate[i][0] = ate[i-1][0]+1;

		if (a[i] == '0') ate[i][1] = 0;
		else ate[i][1] = ate[i-1][1]+1;
	}
 	
 	seg[0].build(1, 0, n);
 	seg[1].build(1, 0, n);

 	seg[0].upd(1, 0, n, 0, b[1] == '1');
 	seg[1].upd(1, 0, n, 0, b[1] == '0');

	for (int i = 1; i <= n; i++)
	{
		dp[i][0] = dp[i][1] = n+1;

		pref[i][0] = pref[i-1][0];
		if (i > 1) pref[i][0] += (b[i] == '1' && b[i-1] == '0');

		pref[i][1] = pref[i-1][1];
		if (i > 1) pref[i][1] += (b[i] == '0' && b[i-1] == '1');
 
		if (a[i] == '0') dp[i][0] = pref[i][0] + seg[0].query(1, 0, n, i-ate[i][0], i-1);
		if (a[i] == '1') dp[i][1] = pref[i][1] + seg[1].query(1, 0, n, i-ate[i][1], i-1);

		dp[i][0] = min(dp[i][0], 1 + pref[i][0] + seg[0].query(1, 0, n, 0, i-ate[i][0]-1));
		dp[i][1] = min(dp[i][1], 1 + pref[i][1] + seg[1].query(1, 0, n, 0, i-ate[i][1]-1));

		seg[0].upd(1, 0, n, i, dp[i][1] - pref[i][0] + (b[i+1] == '1') - 2*(b[i] == '0' && b[i+1] == '1'));
		seg[1].upd(1, 0, n, i, dp[i][0] - pref[i][1] + (b[i+1] == '0') - 2*(b[i] == '1' && b[i+1] == '0'));
	}
 
	printf("%d\n", min(dp[n][0], dp[n][1]));
}

Compilation message (stderr)

lamp.cpp: In function 'int main()':
lamp.cpp:60:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   60 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
lamp.cpp:63:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   63 |   scanf(" %c", &a[i]);
      |   ~~~~~^~~~~~~~~~~~~~
lamp.cpp:66:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   66 |   scanf(" %c", &b[i]);
      |   ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 0 / 4
• Subtask 4: 0 / 49