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Harden sprint4 CLI solvers against input-driven DoS and unbounded allocation #84

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Harden sprint4 CLI solvers against input-driven DoS and unbounded allocation #84

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44 changes: 32 additions & 12 deletions src/main/java/algorithms/sprint4/FindSystem.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,11 +9,17 @@
import java.util.HashSet;
import java.util.Map;
import java.util.StringTokenizer;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;

// https://contest.yandex.ru/contest/24414/run-report/160043341/

class FindSystem {

private static final int MAX_DOCUMENTS = 10_000;
private static final int MAX_QUERIES = 10_000;
private static final int MAX_LINE_LENGTH = 10_000;
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krotname marked this conversation as resolved.

/*
* Принцип работы алгоритма:
* 1) Строим обратный индекс:
Expand Down Expand Up @@ -141,23 +147,24 @@ private static boolean isBetter(int docId1, int score1, int docId2, int score2)
private static void solve() throws Exception {
FastReader reader = new FastReader(System.in);

int n = reader.nextInt();
int n = reader.nextInt(MAX_DOCUMENTS);
String[] docs = new String[n];
for (int i = 0; i < n; i++) {
docs[i] = reader.nextLine();
docs[i] = reader.nextLine(MAX_LINE_LENGTH);
}

HashMap<String, ArrayList<int[]>> index = buildIndex(docs);

int m = reader.nextInt();
StringBuilder out = new StringBuilder();
int m = reader.nextInt(MAX_QUERIES);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));

for (int i = 0; i < m; i++) {
String query = reader.nextLine();
out.append(processQuery(query, index)).append('\n');
String query = reader.nextLine(MAX_LINE_LENGTH);
out.write(processQuery(query, index));
out.newLine();
}

System.out.print(out);
out.flush();
}

private static void test() {
Expand Down Expand Up @@ -205,7 +212,11 @@ public static void main(String[] args) throws Exception {
if (System.getProperty("os.name").startsWith("Windows")) {
test();
} else {
solve();
try {
solve();
} catch (IOException ignored) {
// Invalid or excessive input is rejected without exhausting memory or CPU.
}
}
}
private static class FastReader {
Expand All @@ -229,7 +240,7 @@ private int read() throws IOException {
return buffer[ptr++];
}

int nextInt() throws IOException {
int nextInt(int max) throws IOException {
int c;
do {
c = read();
Expand All @@ -238,15 +249,21 @@ int nextInt() throws IOException {
}
} while (c <= ' ');

int value = 0;
long value = 0;
while (c > ' ') {
if (c < '0' || c > '9') {
throw new IOException("Expected a non-negative integer");
}
value = value * 10 + c - '0';
if (value > max) {
throw new IOException("Input value exceeds limit");
}
c = read();
}
return value;
return (int) value;
}

String nextLine() throws IOException {
String nextLine(int maxLength) throws IOException {
int c = read();

while (c == '\n' || c == '\r') {
Expand All @@ -255,6 +272,9 @@ String nextLine() throws IOException {

StringBuilder sb = new StringBuilder();
while (c != -1 && c != '\n' && c != '\r') {
if (sb.length() == maxLength) {
throw new IOException("Input line exceeds limit");
}
sb.append((char) c);
c = read();
}
Expand Down
61 changes: 47 additions & 14 deletions src/main/java/algorithms/sprint4/Map.java
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Original file line number Diff line number Diff line change
@@ -1,9 +1,12 @@
package algorithms.sprint4;

import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.util.OptionalInt;
import java.util.concurrent.ThreadLocalRandom;

// https://contest.yandex.ru/contest/24414/run-report/160371601/

Expand Down Expand Up @@ -51,6 +54,8 @@ public class Map {
*/

private static final int SIZE = 100_003;
private static final int MAX_COMMANDS = 100_000;
private static final int HASH_SEED = ThreadLocalRandom.current().nextInt();

static class Node {
int key;
Expand All @@ -68,11 +73,9 @@ static class HashTable {
Node[] buckets = new Node[SIZE];

int index(int key) {
int x = key % SIZE;
if (x < 0) {
x += SIZE;
}
return x;
int mixed = key ^ HASH_SEED;
mixed ^= (mixed >>> 16);
return Math.floorMod(mixed, SIZE);
}

void put(int key, int value) {
Expand Down Expand Up @@ -144,8 +147,15 @@ int read() throws IOException {
}

int nextInt() throws IOException {
return nextInt(Integer.MIN_VALUE, Integer.MAX_VALUE);
}

int nextInt(int min, int max) throws IOException {
int c = read();
while (c <= ' ') {
if (c == -1) {
throw new IOException("Unexpected end of input");
}
c = read();
}

Expand All @@ -155,13 +165,24 @@ int nextInt() throws IOException {
c = read();
}

int num = 0;
if (c < '0' || c > '9') {
throw new IOException("Expected integer");
}

long num = 0;
while (c > ' ') {
if (c < '0' || c > '9') {
throw new IOException("Expected integer");
}
num = num * 10 + c - '0';
long signed = sign * num;
if (signed < min || signed > max) {
throw new IOException("Input value exceeds limit");
}
c = read();
}

return num * sign;
return (int) (num * sign);
}

char nextCommand() throws IOException {
Expand All @@ -181,11 +202,19 @@ char nextCommand() throws IOException {
}

public static void main(String[] args) throws Exception {
try {
solve();
} catch (IOException ignored) {
// Invalid or excessive input is rejected without exhausting memory or CPU.
}
}

private static void solve() throws IOException {
Reader reader = new Reader();
HashTable table = new HashTable();
StringBuilder out = new StringBuilder();
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));

int n = reader.nextInt();
int n = reader.nextInt(0, MAX_COMMANDS);

for (int i = 0; i < n; i++) {
char command = reader.nextCommand();
Expand All @@ -195,14 +224,18 @@ public static void main(String[] args) throws Exception {
int value = reader.nextInt();
table.put(key, value);
} else if (command == 'g') {
table.get(key).ifPresentOrElse(out::append, () -> out.append("None"));
out.append(System.lineSeparator());
OptionalInt result = table.get(key);
out.write(result.isPresent() ? String.valueOf(result.getAsInt()) : "None");
out.newLine();
} else if (command == 'd') {
OptionalInt result = table.delete(key);
out.write(result.isPresent() ? String.valueOf(result.getAsInt()) : "None");
out.newLine();
} else {
table.delete(key).ifPresentOrElse(out::append, () -> out.append("None"));
out.append(System.lineSeparator());
throw new IOException("Unknown command");
}
}

System.out.print(out);
out.flush();
}
}
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