Consolidate remaining validated robustness fixes

src/main/java/algorithms/sprint0/Zip.java

@@ -8,15 +8,18 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
+import java.io.StringReader;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
 
 import static algorithms.sprint0.Utils.printList;
-import static algorithms.sprint0.Utils.readList;
 
 public class Zip {
 
+    private static final int MAX_LIST_SIZE = 100_000;
+    private static final int MAX_INPUT_LINE_LENGTH = 1_200_001;
+
     static List<Integer> zip(List<Integer> a, List<Integer> b, int n) {
         if (n < 0) {
             throw new IllegalArgumentException("n >= 0 required");
@@ -34,14 +37,53 @@ static List<Integer> zip(List<Integer> a, List<Integer> b, int n) {
     public static void main(String[] args) throws IOException {
         try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in, StandardCharsets.UTF_8));
              BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out, StandardCharsets.UTF_8))) {
-            String sizeLine = reader.readLine();
-            if (sizeLine == null) {
-                throw new EOFException("Missing list size");
+            try {
+                process(reader, writer);
+            } catch (IllegalArgumentException | EOFException exception) {
+                System.err.println("Invalid input: " + exception.getMessage());
             }
-            int n = parseInt(sizeLine.trim());
-            List<Integer> a = readList(reader);
-            List<Integer> b = readList(reader);
-            printList(zip(a, b, n), writer);
         }
     }
+
+    static void process(BufferedReader reader, BufferedWriter writer) throws IOException {
+        String sizeLine = readBoundedLine(reader);
+        if (sizeLine == null) {
+            throw new EOFException("Missing list size");
+        }
+        int n = parseInt(sizeLine.trim());
+        if (n < 0 || n > MAX_LIST_SIZE) {
+            throw new IllegalArgumentException("List size must be between 0 and " + MAX_LIST_SIZE);
+        }
+        List<Integer> a = parseList(readBoundedLine(reader));
+        List<Integer> b = parseList(readBoundedLine(reader));
+        if (a.size() < n || b.size() < n) {
+            throw new IllegalArgumentException("Each list must contain at least n integers");
+        }
+        printList(zip(a, b, n), writer);
+    }
+
+    private static String readBoundedLine(BufferedReader reader) throws IOException {
+        StringBuilder line = new StringBuilder();
+        int character;
+        while ((character = reader.read()) != -1 && character != '\n' && character != '\r') {
+            if (line.length() == MAX_INPUT_LINE_LENGTH) {
+                throw new IllegalArgumentException("Input line is too long");
+            }
+            line.append((char) character);
+        }
+        if (character == '\r') {
+            reader.mark(1);
+            if (reader.read() != '\n') {
+                reader.reset();
+            }
+        }
+        return character == -1 && line.length() == 0 ? null : line.toString();
+    }
+
+    private static List<Integer> parseList(String line) throws IOException {
+        if (line == null) {
+            throw new EOFException("Missing integer list");
+        }
+        return Utils.readList(new BufferedReader(new StringReader(line)));
+    }
 }

src/main/java/algorithms/sprint1/SleightOfHand.java

@@ -48,18 +48,21 @@ int nextInt() throws IOException {
             return val * sign;
         }
 
-        String next() throws IOException {
+        String next(int maxLength) throws IOException {
             int c;
             do {
                 c = read();
                 if (c == -1) throw new EOFException("Unexpected EOF");
             } while (c <= ' ');
 
-            byte[] tmp = new byte[32];
+            byte[] tmp = new byte[Math.min(32, maxLength)];
             int n = 0;
             while (c > ' ') {
+                if (n == maxLength) {
+                    throw new IOException("Token length exceeds " + maxLength);
+                }
                 if (n == tmp.length) {
-                    byte[] t2 = new byte[tmp.length * 2];
+                    byte[] t2 = new byte[Math.min(maxLength, tmp.length * 2)];
                     System.arraycopy(tmp, 0, t2, 0, tmp.length);
                     tmp = t2;
                 }
@@ -128,14 +131,17 @@ private static void run() throws Exception {
         int[] count = new int[10];
 
         for (int r = 0; r < 4; r++) {
-            StringBuilder row = new StringBuilder(in.next());
+            StringBuilder row = new StringBuilder(in.next(4));
             // На всякий случай, если токенайзер разделит строку (обычно не будет)
             while (row.length() < 4) {
-                row.append(in.next());
+                row.append(in.next(4 - row.length()));
             }
             for (int c = 0; c < 4; c++) {
                 char ch = row.charAt(c);
                 if (ch != '.') {
+                    if (ch < '0' || ch > '9') {
+                        throw new IOException("Invalid grid cell: " + ch);
+                    }
                     count[ch - '0']++;
                 }
             }
@@ -219,7 +225,12 @@ static int solve(int k, int[][] a) {
 
         for (int[] row : a) {
             for (int v : row) {
-                if (v != 0) count[v]++;
+                if (v != 0) {
+                    if (v < 0 || v > 9) {
+                        throw new IllegalArgumentException("Grid values must be between 0 and 9");
+                    }
+                    count[v]++;
+                }
             }
         }
 

src/main/java/algorithms/sprint2/Deque.java

@@ -55,6 +55,8 @@
 public class Deque {
 
     // -------------------- RING BUFFER DEQUE --------------------
+    private static final int MAX_CAPACITY = 100_000;
+
     static final class RingDeque {
         private final int[] a;
         private final int cap;
@@ -63,8 +65,8 @@ static final class RingDeque {
         private int size = 0;
 
         RingDeque(int cap) {
-            this.cap = cap;
-            this.a = new int[cap];
+            this.cap = validateCapacity(cap);
+            this.a = new int[this.cap];
         }
 
         private int next(int i) {
@@ -112,9 +114,19 @@ int popBack() {
         }
     }
 
+    private static int validateCapacity(int cap) {
+        if (cap < 0 || cap > MAX_CAPACITY) {
+            throw new IllegalArgumentException("Deque capacity is out of range");
+        }
+        return cap;
+    }
+
     private static void process(FastIn in, FastOut out) throws Exception {
         int n = in.nextInt();
         int m = in.nextInt();
+        if (n < 0 || n > MAX_CAPACITY) {
+            throw new IllegalArgumentException("Command count is out of range");
+        }
 
         RingDeque dq = new RingDeque(m);
 
@@ -235,6 +247,10 @@ private static void test() throws Exception {
                 )
         );
 
+        // Некорректная емкость отклоняется, а не меняет заявленную семантику дека.
+        assertRejected("2\n-1\npush_back 1\npop_front\n");
+        assertRejected("1\n1000000000\npop_front\n");
+
         // Wrap-around: head/tail должны корректно "перепрыгивать" границу массива
         assertEq(
                 "1\n4\n2\n3\n",
@@ -261,6 +277,15 @@ static void assertEq(String exp, String act) {
         }
     }
 
+    private static void assertRejected(String input) throws Exception {
+        try {
+            solveIO(input);
+            throw new AssertionError("Expected invalid deque capacity to be rejected");
+        } catch (IllegalArgumentException expected) {
+            // Expected validation failure.
+        }
+    }
+
     public static void main(String[] args) throws Exception {
         if (System.getProperty("os.name").startsWith("Windows")) {
             test();

src/main/java/algorithms/sprint4/FindSystem.java

@@ -9,11 +9,18 @@
 import java.util.HashSet;
 import java.util.Map;
 import java.util.StringTokenizer;
+import java.io.BufferedWriter;
+import java.io.OutputStreamWriter;
+import java.nio.charset.StandardCharsets;
 
 // 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;
+
     /*
      * Принцип работы алгоритма:
      * 1) Строим обратный индекс:
@@ -141,23 +148,25 @@ 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, StandardCharsets.UTF_8));
 
         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() {
@@ -229,7 +238,7 @@ private int read() throws IOException {
             return buffer[ptr++];
         }
 
-        int nextInt() throws IOException {
+        int nextInt(int max) throws IOException {
             int c;
             do {
                 c = read();
@@ -238,15 +247,21 @@ 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') {
@@ -255,6 +270,9 @@ 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();
             }