Submission #1324785

#TimeUsernameProblemLanguageResultExecution timeMemory
1324785brendonwRainforest Jumps (APIO21_jumps)C++20
0 / 100
11 ms16068 KiB
#include <bits/stdc++.h>

using namespace std;
const int MAXN = 2e5;
int h[MAXN], prevmx[MAXN], nxtmx[MAXN], jmpup[MAXN][20], jmpright[MAXN][20], idx[MAXN + 1];
int n;

struct segtree {
	int n;
	vector<pair<int, int>> seg;
	segtree() = default;
	segtree(int n) : n(n), seg(2 * n, {-1, -1}) {};
	void update(int i, pair<int, int> val) {
		i += n;
		seg[i] = max(seg[i], val);
		for (; i >>= 1;) {
			seg[i] = max(seg[i << 1], seg[i << 1 | 1]);
		}
	}
	pair<int, int> query(int l, int r) {
		pair<int, int> ans = {-1, -1};
		for (l += n, r += n; l < r; l >>= 1, r >>= 1) {
			if (l & 1) {
				ans = max(ans, seg[l++]);
			}
			if (r & 1) {
				ans = max(ans, seg[--r]);
			}
		}
		return ans;
	}
};

segtree st;
void init(int N, vector<int> H) {
	n = N;
	st = n;
	copy(H.begin(), H.end(), h);
	for (int i = 0; i < n; ++i) {
		st.update(i, {h[i], i});
		idx[h[i]] = i;
	}
	for (int i = 0; i < n; ++i) {
		prevmx[i] = i - 1;
		while (prevmx[i] != -1 && h[prevmx[i]] <= h[i]) {
			prevmx[i] = prevmx[prevmx[i]];
		}
	}
	for (int i = n - 1; i >= 0; --i) {
		nxtmx[i] = i + 1;
		while (nxtmx[i] < n && h[nxtmx[i]] <= h[i]) {
			nxtmx[i] = nxtmx[nxtmx[i]];
		}
	}
	memset(jmpup, -1, sizeof jmpup);
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < 20; ++j) {
			jmpright[i][j] = n;
		}
	}
	for (int val = n; val >= 1; --val) {
		int i = idx[val];
		auto nxt = [&](int x) {
			if (prevmx[x] == -1 && nxtmx[x] == n) {
				return -1;
			} else if (prevmx[x] == -1) {
				return nxtmx[x];
			} else if (nxtmx[x] == n) {
				return prevmx[x];
			} else if (h[prevmx[x]] > h[nxtmx[x]]) {
				return prevmx[x];
			} else {
				return nxtmx[x];
			}
		};
		jmpup[i][0] = nxt(i);
		int j = 0;
		while (jmpup[i][j] != -1) {
			jmpup[i][j + 1] = jmpup[jmpup[i][j]][j];
			j++;
		}
		jmpright[i][0] = nxtmx[i];
		j = 0;
		while (jmpright[i][j] < n) {
			jmpright[i][j + 1] = jmpright[jmpright[i][j]][j];
			j++;
		}
	}
}

int minimum_jumps(int A, int B, int C, int D) {
	int mncnt = n;
	for (int i = C; i <= D; ++i) {
		pair<int, int> val = st.query(max(prevmx[i] + 1, A), B + 1);
		if (val.first == -1) {
			continue;
		}
		int x = val.second;
		int cnt = 0;
		while (jmpup[x][0] != -1 && h[jmpup[x][0]] < h[i]) {
			int j = 0;
			for (; 1 << j < n; ++j) {
				if (jmpup[x][j] == -1 || h[jmpup[x][j]] >= h[i]) {
					break;
				}
			}
			cnt += 1 << (--j);
			x = jmpup[x][j];
		}
		while (x != i) {
			cnt++;
			x = jmpright[x][0];
		}
		//		while (jmpright[x][0] < n && h[jmpright[x][0]] < h[i]) {
//			int j = 0;
//			for (; 1 << j < n; ++j) {
//				if (jmpright[x][j] == -1 || h[jmpright[x][j]] >= h[i]) {
//					break;
//				}
//			}
//			cnt += 1 << (--j);
//			x = jmpright[x][j];
//		}
		cnt++;
		mncnt = min(mncnt, cnt);
	}
	return mncnt == n ? -1 : mncnt;
}
#ifndef EVAL
int main() {
	init(7, {3, 2, 1, 6, 4, 5, 7});
	cout << minimum_jumps(4, 4, 6, 6) << '\n';
	cout << minimum_jumps(1, 3, 5, 6) << '\n';
	cout << minimum_jumps(0, 0, 2, 2) << '\n';
//	init(7, {4, 1, 7, 6, 3, 5, 2});
//	cout << minimum_jumps(1, 2, 3, 6) << '\n';
//	cout << minimum_jumps(0, 3, 4, 6) << '\n';
//	cout << minimum_jumps(0, 1, 2, 2) << '\n';
	return 0;
}
#endif
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