結果
問題 | No.778 クリスマスツリー |
ユーザー |
|
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 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 12 |
ソースコード
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 による Range Sum Query*/static class BIT {// [0,n-1]private int[] bit;private int n;/*** n 個の要素を持つBITを生成する** @param n 要素数*/BIT(int n) {this.n = n;bit = new int[this.n];}/*** i 番目の要素に x を足す** @param i 対象となる要素(1-indexed)* @param x 追加する値*/void add(int i, int x) {while (i <= n) {bit[i - 1] += x;i += i & (-i);}}/*** 指定した範囲の合計値を返す** @param i 範囲の上界。[1,i](1-indexed)* @return 指定された範囲の合計値*/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);}}}