Submission #34571

#	Time	Username	Problem	Language	Result	Execution time	Memory
34571		sinhriv	Watching (JOI13_watching)	C++14	50 / 100	1000 ms	96744 KiB

watching

#include <bits/stdc++.h>

using namespace std;

const int N = 2202;

int n, p, q;
int a[N];
int f[N][N];

struct SegmentTreeMin{
	int it[N * 4];

	#define mid ((l + r) >> 1)

	void build(int x, int l, int r){
		it[x] = 1e9;
		if(l == r) {
			return;
		}
		build(x + x, l, mid);
		build(x + x + 1, mid + 1, r);
	}

	void modify(int x, int l, int r, int pos, int val){
		if(l > pos || r < pos) return;
		it[x] = min(it[x], val);
		if(l == r) return;
		modify(x + x, l, mid, pos, val);
		modify(x + x + 1, mid + 1, r, pos, val);
	}

	int query(int x, int l, int r, int u, int v){
		if(l > v || r < u) return 1e9;
		if(l >= u && r <= v) return it[x];
		return min(query(x + x, l, mid, u, v), query(x + x + 1, mid + 1, r, u, v));
	}
}g[N];

int main(){
	if(fopen("1.inp", "r")){
		freopen("1.inp", "r", stdin);
	}

	scanf("%d%d%d", &n, &p, &q);

	for(int i = 1; i <= n; ++i){
		scanf("%d", a + i);
	}

	p = min(p, n);
	q = min(q, n);

	sort(a + 1, a + n + 1);

	int low = 1, high = 1e9, ans = 1e9;

	while(low <= high){
		int w = (low + high) >> 1;
	
		memset(f, 60, sizeof f);


		f[0][0] = 0;
		for(int i = 0; i <= p; ++i){
			g[i].build(1, 0, n);
		}

		g[0].modify(1, 0, n, 0, 0);

		bool ok = false, debug = false;


		
		for(int i = 1; i <= n; ++i){
			for(int j = 0; j <= min(i, p); ++j){
				if(j > 0){
					int pos = lower_bound(a + 1, a + n + 1, a[i] - w + 1) - a;
					f[i][j] = g[j - 1].query(1, 0, n, pos - 1, i);
				}
				int pos = lower_bound(a + 1, a + n + 1, a[i] - w - w + 1) - a;
				f[i][j] = min(f[i][j], g[j].query(1, 0, n, pos - 1, i) + 1);


				if(i == n && f[i][j] <= q){
					ok = true;
				}
				g[j].modify(1, 0, n, i, f[i][j]);
			}
		}



		if(ok == false){
			low = w + 1;
		}
		else{
			ans = w;
			high = w - 1;
		}
	}

	cout << ans;

	return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:71:20: warning: unused variable 'debug' [-Wunused-variable]
   bool ok = false, debug = false;
                    ^
watching.cpp:42:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   freopen("1.inp", "r", stdin);
                               ^
watching.cpp:45:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d", &n, &p, &q);
                             ^
watching.cpp:48:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", a + i);
                     ^

• Subtask 1: 50 / 50
• Subtask 2: 0 / 50