Submission #1029092

#	Time	Username	Problem	Language	Result	Execution time	Memory
1029092		AmirAli_H1	Ancient Books (IOI17_books)	C++17	100 / 100	164 ms	32852 KiB

books

// In the name of Allah
 
#include <bits/stdc++.h>
#include "books.h"
using namespace std;
 
typedef		long long int			ll;
typedef		long double				ld;
typedef		pair<int, int>			pii;
typedef		pair<ll, ll>			pll;
typedef		complex<ld>				cld;
 
#define		all(x)					(x).begin(),(x).end()
#define		len(x)					((ll) (x).size())
#define		F						first
#define		S						second
#define		pb						push_back
#define		sep						' '
#define		endl					'\n'
#define		Mp						make_pair
#define		kill(x)					cout << x << '\n', exit(0)
#define		set_dec(x)				cout << fixed << setprecision(x);
#define		file_io(x,y)			freopen(x, "r", stdin); freopen(y, "w", stdout);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
 
const int maxn = 1e6 + 4;
const int oo = 1e9 + 7;
 
int n; ll res;
int A[maxn], mark[maxn];
int sm[maxn], mn, mx;
int dis[maxn]; deque<int> dq;
 
void dfs(int v) {
	mark[v] = 1;
	mn = min(mn, v); mx = max(mx, v);
	if (!mark[A[v]]) dfs(A[v]);
}

void bfs01(int s) {
	fill(mark, mark + n, 0); fill(dis, dis + n, oo);
	dis[s] = 0; dq.pb(s);
	while (!dq.empty()) {
		int v = dq.front(); dq.pop_front();
		if (mark[v]) continue;
		mark[v] = 1;
		if (v - 1 >= 0) {
			int u = v - 1, w = (abs(v - s) < abs(u - s));
			if (dis[v] + w < dis[u]) {
				dis[u] = dis[v] + w;
				if (w == 0) dq.push_front(u);
				else dq.pb(u);
			}
		}
		if (v + 1 < n) {
			int u = v + 1, w = (abs(v - s) < abs(u - s));
			if (dis[v] + w < dis[u]) {
				dis[u] = dis[v] + w;
				if (w == 0) dq.push_front(u);
				else dq.pb(u);
			}
		}
		int u = A[v], w = 0;
		if (dis[v] + w < dis[u]) {
			dis[u] = dis[v] + w;
			if (w == 0) dq.push_front(u);
			else dq.pb(u);
		}
	}
}
 
ll minimum_walk(vector<int> p, int s) {
	n = len(p); res = 0;
	for (int i = 0; i < n; i++) {
		A[i] = p[i];
		res += abs(i - A[i]);
	}
	
	int m1 = s, m2 = s;
	for (int i = 0; i < n; i++) {
		if (A[i] != i) {
			m1 = min(m1, i); m2 = max(m2, i);
		}
		
		if (!mark[i]) {
			mn = i; mx = i;
			dfs(i);
			sm[mn]++; sm[mx]--;
		}
	}
	for (int i = 1; i < n; i++) {
		sm[i] += sm[i - 1];
	}
	
	int l = s, r = s;
	for (int i = s; i < m2; i++) {
		if (sm[i] != 0) r = i + 1;
		else break;
	}
	for (int i = s - 1; i >= m1; i--) {
		if (sm[i] != 0) l = i;
		else break;
	}
	
	for (int i = m1; i < m2; i++) {
		if (sm[i] == 0) res += 2;
	}
	
	bfs01(s);
	res += 2 * dis[l];
	return res;
}

Compilation message (stderr)

books.cpp: In function 'll minimum_walk(std::vector<int>, int)':
books.cpp:95:13: warning: variable 'r' set but not used [-Wunused-but-set-variable]
   95 |  int l = s, r = s;
      |             ^

• Subtask 1: 12 / 12
• Subtask 2: 10 / 10
• Subtask 3: 28 / 28
• Subtask 4: 20 / 20
• Subtask 5: 30 / 30