Submission #1324711

#TimeUsernameProblemLanguageResultExecution timeMemory
1324711brendonwRainforest Jumps (APIO21_jumps)C++20
0 / 100
571 ms1114112 KiB
#include <bits/stdc++.h>

using namespace std;
const int MAXN = 2e5;
int h[MAXN], prevmx[MAXN], nxtmx[MAXN], idx[MAXN];
vector<vector<int>> dp;
int n;
void init(int N, vector<int> H) {
	n = N;
	dp.assign(n, vector<int>(n, n));
	copy(H.begin(), H.end(), h);
	for (int i = 0; i < n; ++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]];
		}
	}
	for (int i = 0; i < n; ++i) {
		dp[i][i] = 0;
		for (int val = h[i] - 1; val >= 0; --val) {
			int j = idx[val];
			if (prevmx[j] != -1) {
				dp[i][j] = min(dp[i][j], 1 + dp[i][prevmx[j]]);
			}
			if (nxtmx[j] != -1) {
				dp[i][j] = min(dp[i][j], 1 + dp[i][nxtmx[j]]);
			}
		}
	}
}

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