結果

問題 No.778 クリスマスツリー
ユーザー Grenache
提出日時 2019-05-02 20:31:00
言語 Java
(openjdk 23)
結果
AC  
実行時間 436 ms / 2,000 ms
コード長 5,347 bytes
コンパイル時間 3,923 ms
コンパイル使用メモリ 80,008 KB
実行使用メモリ 82,532 KB
最終ジャッジ日時 2024-10-14 01:59:43
合計ジャッジ時間 8,215 ms
ジャッジサーバーID
(参考情報)
judge5 / judge4
このコードへのチャレンジ
(要ログイン)
ファイルパターン 結果
sample AC * 3
other AC * 12
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

import java.io.*;
import java.util.*;
public class Main_yukicoder778 {
private static Scanner sc;
private static Printer pr;
private static void solve() {
int n = sc.nextInt();
int[] a = new int[n - 1];
for (int i = 0; i < n - 1; i++) {
a[i] = sc.nextInt();
}
List<List<Integer>> edges = new ArrayList<>(n);
for (int i = 0; i < n; i++) {
edges.add(new ArrayList<>());
}
for (int i = 0; i < n - 1; i++) {
edges.get(a[i]).add(i + 1);
}
BIT bit = new BIT(n);
long ans = 0;
boolean[] used = new boolean[n];
Deque<Integer> st = new ArrayDeque<>();
st.push(0);
while (!st.isEmpty()) {
int e = st.peek();
if (used[e]) {
st.pop();
ans += bit.query(e);
bit.add(e + 1, -1);
continue;
}
used[e] = true;
bit.add(e + 1, 1);
for (int next : edges.get(e)) {
st.push(next);
}
}
pr.println(ans);
}
/**
* Binary Indexed Tree Range Sum Query
*/
static class BIT {
// [0,n-1]
private int[] bit;
private int n;
/**
* n BIT
*
* @param n
*/
BIT(int n) {
this.n = n;
bit = new int[this.n];
}
/**
* i x
*
* @param i (1-indexed)
* @param x
*/
void add(int i, int x) {
while (i <= n) {
bit[i - 1] += x;
i += i & (-i);
}
}
/**
*
*
* @param i [1,i](1-indexed)
* @return
*/
int query(int i) {
int sum = 0;
while (i > 0) {
sum += bit[i - 1];
i -= i & (-i);
}
return sum;
}
}
// ---------------------------------------------------
public static void main(String[] args) {
sc = new Scanner(System.in);
pr = new Printer(System.out);
solve();
pr.close();
sc.close();
}
static class Scanner {
BufferedReader br;
Scanner (InputStream in) {
br = new BufferedReader(new InputStreamReader(in));
}
private boolean isPrintable(int ch) {
return ch >= '!' && ch <= '~';
}
private boolean isCRLF(int ch) {
return ch == '\n' || ch == '\r' || ch == -1;
}
private int nextPrintable() {
try {
int ch;
while (!isPrintable(ch = br.read())) {
if (ch == -1) {
throw new NoSuchElementException();
}
}
return ch;
} catch (IOException e) {
throw new NoSuchElementException();
}
}
String next() {
try {
int ch = nextPrintable();
StringBuilder sb = new StringBuilder();
do {
sb.appendCodePoint(ch);
} while (isPrintable(ch = br.read()));
return sb.toString();
} catch (IOException e) {
throw new NoSuchElementException();
}
}
int nextInt() {
try {
// parseInt from Integer.parseInt()
boolean negative = false;
int res = 0;
int limit = -Integer.MAX_VALUE;
int radix = 10;
int fc = nextPrintable();
if (fc < '0') {
if (fc == '-') {
negative = true;
limit = Integer.MIN_VALUE;
} else if (fc != '+') {
throw new NumberFormatException();
}
fc = br.read();
}
int multmin = limit / radix;
int ch = fc;
do {
int digit = ch - '0';
if (digit < 0 || digit >= radix) {
throw new NumberFormatException();
}
if (res < multmin) {
throw new NumberFormatException();
}
res *= radix;
if (res < limit + digit) {
throw new NumberFormatException();
}
res -= digit;
} while (isPrintable(ch = br.read()));
return negative ? res : -res;
} catch (IOException e) {
throw new NoSuchElementException();
}
}
long nextLong() {
try {
// parseLong from Long.parseLong()
boolean negative = false;
long res = 0;
long limit = -Long.MAX_VALUE;
int radix = 10;
int fc = nextPrintable();
if (fc < '0') {
if (fc == '-') {
negative = true;
limit = Long.MIN_VALUE;
} else if (fc != '+') {
throw new NumberFormatException();
}
fc = br.read();
}
long multmin = limit / radix;
int ch = fc;
do {
int digit = ch - '0';
if (digit < 0 || digit >= radix) {
throw new NumberFormatException();
}
if (res < multmin) {
throw new NumberFormatException();
}
res *= radix;
if (res < limit + digit) {
throw new NumberFormatException();
}
res -= digit;
} while (isPrintable(ch = br.read()));
return negative ? res : -res;
} catch (IOException e) {
throw new NoSuchElementException();
}
}
float nextFloat() {
return Float.parseFloat(next());
}
double nextDouble() {
return Double.parseDouble(next());
}
String nextLine() {
try {
int ch;
while (isCRLF(ch = br.read())) {
if (ch == -1) {
throw new NoSuchElementException();
}
}
StringBuilder sb = new StringBuilder();
do {
sb.appendCodePoint(ch);
} while (!isCRLF(ch = br.read()));
return sb.toString();
} catch (IOException e) {
throw new NoSuchElementException();
}
}
void close() {
try {
br.close();
} catch (IOException e) {
// throw new NoSuchElementException();
}
}
}
static class Printer extends PrintWriter {
Printer(OutputStream out) {
super(out);
}
}
}
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