結果
| 問題 |
No.19 ステージの選択
|
| コンテスト | |
| ユーザー |
 narushimas
|
| 提出日時 | 2020-09-25 18:11:14 |
| 言語 | Java (openjdk 23) |
| 結果 |
AC
|
| 実行時間 | 56 ms / 5,000 ms |
| コード長 | 13,275 bytes |
| コンパイル時間 | 2,927 ms |
| コンパイル使用メモリ | 92,068 KB |
| 実行使用メモリ | 37,348 KB |
| 最終ジャッジ日時 | 2024-06-28 05:54:38 |
| 合計ジャッジ時間 | 5,385 ms |
|
ジャッジサーバーID （参考情報） |
judge4 / judge5 |
（要ログイン）
| ファイルパターン | 結果 |
|---|---|
| other | AC * 24 |
ソースコード
import java.io.*;
import java.util.*;
class SCC {
static class Edge {
int from, to;
public Edge(int from, int to) {
this.from = from;
this.to = to;
}
}
final int n;
int m;
final java.util.ArrayList<Edge> unorderedEdges;
final int[] start;
final int[] ids;
boolean hasBuilt = false;
public SCC(int n) {
this.n = n;
this.unorderedEdges = new java.util.ArrayList<>();
this.start = new int[n + 1];
this.ids = new int[n];
}
public void addEdge(int from, int to) {
rangeCheck(from);
rangeCheck(to);
unorderedEdges.add(new Edge(from, to));
start[from + 1]++;
this.m++;
}
public int id(int i) {
if (!hasBuilt) {
throw new UnsupportedOperationException("Graph hasn't been built.");
}
rangeCheck(i);
return ids[i];
}
public int[][] build() {
for (int i = 1; i <= n; i++) {
start[i] += start[i - 1];
}
Edge[] orderedEdges = new Edge[m];
int[] count = new int[n + 1];
System.arraycopy(start, 0, count, 0, n + 1);
for (Edge e : unorderedEdges) {
orderedEdges[count[e.from]++] = e;
}
int nowOrd = 0;
int groupNum = 0;
int k = 0;
// parent
int[] par = new int[n];
int[] vis = new int[n];
int[] low = new int[n];
int[] ord = new int[n];
java.util.Arrays.fill(ord, -1);
// u = lower32(stack[i]) : visiting vertex
// j = upper32(stack[i]) : jth child
long[] stack = new long[n];
// size of stack
int ptr = 0;
// non-recursional DFS
for (int i = 0; i < n; i++) {
if (ord[i] >= 0)
continue;
par[i] = -1;
// vertex i, 0th child.
stack[ptr++] = 0l << 32 | i;
// stack is not empty
while (ptr > 0) {
// last element
long p = stack[--ptr];
// vertex
int u = (int) (p & 0xffff_ffffl);
// jth child
int j = (int) (p >>> 32);
if (j == 0) { // first visit
low[u] = ord[u] = nowOrd++;
vis[k++] = u;
}
if (start[u] + j < count[u]) { // there are more children
// jth child
int to = orderedEdges[start[u] + j].to;
// incr children counter
stack[ptr++] += 1l << 32;
if (ord[to] == -1) { // new vertex
stack[ptr++] = 0l << 32 | to;
par[to] = u;
} else { // backward edge
low[u] = Math.min(low[u], ord[to]);
}
} else { // no more children (leaving)
while (j-- > 0) {
int to = orderedEdges[start[u] + j].to;
// update lowlink
if (par[to] == u)
low[u] = Math.min(low[u], low[to]);
}
if (low[u] == ord[u]) { // root of a component
while (true) { // gathering verticies
int v = vis[--k];
ord[v] = n;
ids[v] = groupNum;
if (v == u)
break;
}
groupNum++; // incr the number of components
}
}
}
}
for (int i = 0; i < n; i++) {
ids[i] = groupNum - 1 - ids[i];
}
int[] counts = new int[groupNum];
for (int x : ids)
counts[x]++;
int[][] groups = new int[groupNum][];
for (int i = 0; i < groupNum; i++) {
groups[i] = new int[counts[i]];
}
for (int i = 0; i < n; i++) {
int cmp = ids[i];
groups[cmp][--counts[cmp]] = i;
}
hasBuilt = true;
return groups;
}
private void rangeCheck(int i) {
if (i < 0 || i >= n) {
throw new IndexOutOfBoundsException(String.format("Index %d out of bounds for length %d", i, n));
}
}
}
public class Main {
static void solve() {
int n = ni();
var scc = new SCC(n);
List<Integer>[] next = new ArrayList[n];
for(int i=0;i<n;i++) next[i] = new ArrayList<>();
double[] l = new double[n];
for(int i=0;i<n;i++) {
l[i] = ni();
int from = ni()-1;
next[from].add(i);
scc.addEdge(from, i);
}
var res = scc.build();
double ans = 0;
boolean[] clear = new boolean[n];
for(int i=0;i<res.length;i++) {
double min = linf;
boolean ok = false;
for(int t : res[i]) {
if(clear[t])ok = true;
}
for(int t : res[i]) {
min = min(min, l[t]);
ans += l[t];
for(int to : next[t]) {
clear[to] = true;
}
}
if(!ok)ans += min;
}
ans /= 2;
out.println(ans);
}
//constants
static final int inf = Integer.MAX_VALUE / 2;
static final long linf = Long.MAX_VALUE / 3;
static final double dinf = Double.MAX_VALUE / 3;
static final long mod = (long) 1e9 + 7;
static final int[] dx = { -1, 0, 1, 0 }, dy = { 0, -1, 0, 1 }, dx8 = { -1, -1, -1, 0, 0, 1, 1, 1 },
dy8 = { -1, 0, 1, -1, 1, -1, 0, 1 };
static final double eps = 1e-10;
//libraries
static long[] cum(int a[]) {
long[] cum = new long[a.length + 1];
for (int i = 0; i < a.length; i++)
cum[i + 1] = cum[i] + a[i];
return cum;
}
static long[] cum(long a[]) {
long[] cum = new long[a.length + 1];
for (int i = 0; i < a.length; i++)
cum[i + 1] = cum[i] + a[i];
return cum;
}
static void reverse(int ar[]) {
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
int t = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = t;
}
}
static void reverse(long ar[]) {
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
long t = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = t;
}
}
static void reverse(double ar[]) {
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
double t = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = t;
}
}
static void reverse(char ar[]) {
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
char t = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = t;
}
}
static String getReverse(String s) {
StringBuilder sb = new StringBuilder(s);
return sb.reverse().toString();
}
static <T> void reverse(T[] ar) {
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
T t = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = t;
}
}
static int[] concat(int x, int arr[]) {
int ret[] = new int[arr.length + 1];
System.arraycopy(arr, 0, ret, 1, ret.length - 1);
ret[0] = x;
return ret;
}
static int[] concat(int arr[], int x) {
int ret[] = new int[arr.length + 1];
System.arraycopy(arr, 0, ret, 0, ret.length - 1);
ret[ret.length - 1] = x;
return ret;
}
static long[] concat(long x, long arr[]) {
long ret[] = new long[arr.length + 1];
System.arraycopy(arr, 0, ret, 1, ret.length - 1);
ret[0] = x;
return ret;
}
static long[] concat(long arr[], long x) {
long ret[] = new long[arr.length + 1];
System.arraycopy(arr, 0, ret, 0, ret.length - 1);
ret[ret.length - 1] = x;
return ret;
}
static char[] concat(char x, char arr[]) {
char ret[] = new char[arr.length + 1];
System.arraycopy(arr, 0, ret, 0, ret.length - 1);
ret[ret.length - 1] = x;
return ret;
}
static char[] concat(char arr[], char x) {
char ret[] = new char[arr.length + 1];
System.arraycopy(arr, 0, ret, 0, ret.length - 1);
ret[ret.length - 1] = x;
return ret;
}
static int max(int x, int y) {
return Math.max(x, y);
}
static int min(int x, int y) {
return Math.min(x, y);
}
static int max(int x, int y, int z) {
x = Math.max(x, y);
x = Math.max(x, z);
return x;
}
static int min(int x, int y, int z) {
x = Math.min(x, y);
x = Math.min(x, z);
return x;
}
static long max(long x, long y) {
return Math.max(x, y);
}
static long min(long x, long y) {
return Math.min(x, y);
}
static long max(long x, long y, long z) {
x = Math.max(x, y);
x = Math.max(x, z);
return x;
}
static long min(long x, long y, long z) {
x = Math.min(x, y);
x = Math.min(x, z);
return x;
}
static double max(double x, double y) {
return Math.max(x, y);
}
static double min(double x, double y) {
return Math.min(x, y);
}
static double max(double x, double y, double z) {
x = Math.max(x, y);
x = Math.max(x, z);
return x;
}
static double min(double x, double y, double z) {
x = Math.min(x, y);
x = Math.min(x, z);
return x;
}
static void sort(int[] ar) {
Arrays.sort(ar);
}
static void sort(long[] ar) {
Arrays.sort(ar);
}
static void sort(double[] ar) {
Arrays.sort(ar);
}
static void sort(char[] ar) {
Arrays.sort(ar);
}
static void rsort(int[] ar) {
Arrays.sort(ar);
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
int tmp = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = tmp;
}
}
static void rsort(long[] ar) {
Arrays.sort(ar);
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
long tmp = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = tmp;
}
}
static void rsort(double[] ar) {
Arrays.sort(ar);
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
double tmp = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = tmp;
}
}
static void rsort(char[] ar) {
Arrays.sort(ar);
int len = ar.length;
for (int i = 0; i < len / 2; i++) {
char tmp = ar[i];
ar[i] = ar[len - 1 - i];
ar[len - 1 - i] = tmp;
}
}
static void fill(int arr[], int x) {
Arrays.fill(arr, x);
}
static void fill(long arr[], long x) {
Arrays.fill(arr, x);
}
static void fill(boolean arr[], boolean x) {
Arrays.fill(arr, x);
}
static void fill(double arr[], double x) {
Arrays.fill(arr, x);
}
static void fill(int arr[][], int x) {
for (int i = 0; i < arr.length; i++)
Arrays.fill(arr[i], x);
}
static void fill(long arr[][], long x) {
for (int i = 0; i < arr.length; i++)
Arrays.fill(arr[i], x);
}
static void fill(double arr[][], double x) {
for (int i = 0; i < arr.length; i++)
Arrays.fill(arr[i], x);
}
static void fill(boolean arr[][], boolean x) {
for (int i = 0; i < arr.length; i++)
Arrays.fill(arr[i], x);
}
//MOD culc
static long plus(long x, long y) {
long res = (x + y) % mod;
return res < 0 ? res + mod : res;
}
static long sub(long x, long y) {
long res = (x - y) % mod;
return res < 0 ? res + mod : res;
}
static long mul(long x, long y) {
long res = (x * y) % mod;
return res < 0 ? res + mod : res;
}
static long div(long x, long y) {
long res = x * pow(y, mod - 2) % mod;
return res < 0 ? res + mod : res;
}
static long pow(long x, long y) {
if (y < 0)
return 0;
if (y == 0)
return 1;
if (y % 2 == 1)
return (x * pow(x, y - 1)) % mod;
long root = pow(x, y / 2);
return root * root % mod;
}
public static void main(String[] args) throws Exception {
is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
out = new PrintWriter(System.out);
solve();
out.flush();
}
//input
static InputStream is;
static PrintWriter out;
static String INPUT = "";
private static byte[] inbuf = new byte[1024];
static int lenbuf = 0, ptrbuf = 0;
private static int readByte() {
if (lenbuf == -1)
throw new InputMismatchException();
if (ptrbuf >= lenbuf) {
ptrbuf = 0;
try {
lenbuf = is.read(inbuf);
} catch (IOException e) {
throw new InputMismatchException();
}
if (lenbuf <= 0)
return -1;
}
return inbuf[ptrbuf++];
}
private static boolean isSpaceChar(int c) {
return !(c >= 33 && c <= 126);
}
private static int skip() {
int b;
while ((b = readByte()) != -1 && isSpaceChar(b))
;
return b;
}
@SuppressWarnings("unused")
private static double nd() {
return Double.parseDouble(ns());
}
@SuppressWarnings("unused")
private static char nc() {
return (char) skip();
}
private static String ns() {
int b = skip();
StringBuilder sb = new StringBuilder();
while (!(isSpaceChar(b))) {
sb.appendCodePoint(b);
b = readByte();
}
return sb.toString();
}
private static char[] ns(int n) {
char[] buf = new char[n];
int b = skip(), p = 0;
while (p < n && !(isSpaceChar(b))) {
buf[p++] = (char) b;
b = readByte();
}
return n == p ? buf : Arrays.copyOf(buf, p);
}
@SuppressWarnings("unused")
private static char[][] nm(int n, int m) {
char[][] map = new char[n][];
for (int i = 0; i < n; i++)
map[i] = ns(m);
return map;
}
@SuppressWarnings("unused")
private static int[] na(int n) {
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = ni();
return a;
}
@SuppressWarnings("unused")
private static long[] nla(int n) {
long[] a = new long[n];
for (int i = 0; i < n; i++)
a[i] = nl();
return a;
}
@SuppressWarnings("unused")
private static int[][] na(int n, int m) {
int[][] res = new int[n][m];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
res[i][j] = ni();
}
}
return res;
}
@SuppressWarnings("unused")
private static long[][] nla(int n, int m) {
long[][] res = new long[n][m];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
res[i][j] = nl();
}
}
return res;
}
private static int ni() {
int num = 0, b;
boolean minus = false;
while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
;
if (b == '-') {
minus = true;
b = readByte();
}
while (true) {
if (b >= '0' && b <= '9') {
num = num * 10 + (b - '0');
} else {
return minus ? -num : num;
}
b = readByte();
}
}
private static long nl() {
long num = 0;
int b;
boolean minus = false;
while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
;
if (b == '-') {
minus = true;
b = readByte();
}
while (true) {
if (b >= '0' && b <= '9') {
num = num * 10 + (b - '0');
} else {
return minus ? -num : num;
}
b = readByte();
}
}
}