USACO 2017 February Contest, Platinum Problem 2. Why Did the Cow Cross the Road II

原题下载

USACO2017-FEB-P2

答案:

import java.io.*;
import java.util.*;
public class nocross {

public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new FileReader("nocross.in"));
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("nocross.out")));
int n = Integer.parseInt(br.readLine());
int[] l = new int[n];
for(int i = 0; i < n; i++) {
l[i] = Integer.parseInt(br.readLine())-1;
}
int[] locOf = new int[n];
for(int i = 0; i < n; i++) {
locOf[Integer.parseInt(br.readLine()) - 1] = i;
}
RangeTree dp = new RangeTree(n+1);
for(int i = 0; i < n; i++) {
ArrayList<Integer> indices = new ArrayList<Integer>();
for(int a = Math.max(0, l[i] - 4); a < Math.min(n, l[i] + 5); a++) {
indices.add(locOf[a]);
}
Collections.sort(indices);
for(int a = indices.size()-1; a >= 0; a--) {
dp.update(indices.get(a)+1, dp.query(0, indices.get(a)) + 1);
}
}
pw.println(dp.query(0, n));
pw.close();
}

static class RangeTree {
int[] leaf;
int size;
public RangeTree(int n) {
leaf = new int[4*n];
size = n;
}
public void update(int index, int val) {
update(1, 0, size-1, index, val);
}
private void update(int index, int l, int r, int i, int v) {
if(l == r) {
leaf[index] = v;
}
else {
int m = (l+r)/2;
if(i <= m) {
update(2*index, l, m, i, v);
}
else {
update(2*index+1, m+1, r, i, v);
}
leaf[index] = Math.max(leaf[2*index], leaf[2*index+1]);
}
}
public int query(int l, int r) {
return query(1, 0, size-1, l, r);
}
public int query(int index, int l, int r, int lhs, int rhs) {
if(l >= lhs && r <= rhs) {
return leaf[index];
}
int ret = 0;
int m = (l+r)/2;
if(m >= lhs) {
ret = Math.max(ret, query(2*index, l, m, lhs, rhs));
}
if(m+1 <= rhs) {
ret = Math.max(ret, query(2*index+1, m+1, r, lhs, rhs));
}
return ret;
}
}

}

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