結果

問題 No.778 クリスマスツリー
ユーザー hiromi_ayase
提出日時 2018-12-25 00:21:32
言語 Java
(openjdk 23)
結果
AC  
実行時間 428 ms / 2,000 ms
コード長 3,745 bytes
コンパイル時間 2,394 ms
コンパイル使用メモリ 82,548 KB
実行使用メモリ 91,748 KB
最終ジャッジ日時 2024-10-14 01:51:15
合計ジャッジ時間 7,276 ms
ジャッジサーバーID
(参考情報)
judge4 / judge3
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

public class Main {
private static void solve() {
int n = ni();
int[] a = new int[n];
a[0] = -1;
for (int i = 0; i < n - 1; i ++) {
a[i + 1] = ni();
}
int[][] g = parentToG(a);
int[] ft = new int[n + 1];
long ret = dfs(0, -1, g, ft);
System.out.println(ret);
}
private static long dfs(int i, int j, int[][] g, int[] ft) {
long ret = sumFenwick(ft, i);
addFenwick(ft, i, 1);
for (int to : g[i]) {
if (to == j) continue;
ret += dfs(to, i, g, ft);
}
addFenwick(ft, i, -1);
return ret;
}
public static void addFenwick(int[] ft, int i, int v)
{
if(v == 0 || i < 0)return;
int n = ft.length;
for(i++;i < n;i += i&-i)ft[i] += v;
}
public static int sumFenwick(int[] ft, int i)
{
int sum = 0;
for(i++;i > 0;i -= i&-i)sum += ft[i];
return sum;
}
public static int[][] parentToG(int[] par)
{
int n = par.length;
int[] ct = new int[n];
for(int i = 0;i < n;i++){
if(par[i] >= 0){
ct[i]++;
ct[par[i]]++;
}
}
int[][] g = new int[n][];
for(int i = 0;i < n;i++){
g[i] = new int[ct[i]];
}
for(int i = 0;i < n;i++){
if(par[i] >= 0){
g[par[i]][--ct[par[i]]] = i;
g[i][--ct[i]] = par[i];
}
}
return g;
}
public static void main(String[] args) {
new Thread(null, new Runnable() {
@Override
public void run() {
long start = System.currentTimeMillis();
String debug = args.length > 0 ? args[0] : null;
if (debug != null) {
try {
is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
solve();
out.flush();
tr((System.currentTimeMillis() - start) + "ms");
}
}, "", 64000000).start();
}
private static java.io.InputStream is = System.in;
private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
private static java.util.StringTokenizer tokenizer = null;
private static java.io.BufferedReader reader;
public static String next() {
while (tokenizer == null || !tokenizer.hasMoreTokens()) {
try {
tokenizer = new java.util.StringTokenizer(reader.readLine());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return tokenizer.nextToken();
}
private static double nd() {
return Double.parseDouble(next());
}
private static long nl() {
return Long.parseLong(next());
}
private static int[] na(int n) {
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = ni();
return a;
}
private static char[] ns() {
return next().toCharArray();
}
private static long[] nal(int n) {
long[] a = new long[n];
for (int i = 0; i < n; i++)
a[i] = nl();
return a;
}
private static int[][] ntable(int n, int m) {
int[][] table = new int[n][m];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[i][j] = ni();
}
}
return table;
}
private static int[][] nlist(int n, int m) {
int[][] table = new int[m][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[j][i] = ni();
}
}
return table;
}
private static int ni() {
return Integer.parseInt(next());
}
private static void tr(Object... o) {
if (is != System.in)
System.out.println(java.util.Arrays.deepToString(o));
}
}
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