From 958fb4e7db34f9dc2494612e39e7060254156145 Mon Sep 17 00:00:00 2001
From: Andrei Ovcharenko <a@krot.name>
Date: Fri, 31 Jul 2026 17:45:08 +0300
Subject: [PATCH] Validate deque capacity before allocation

---
 src/main/java/algorithms/sprint2/Deque.java | 34 +++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/main/java/algorithms/sprint2/Deque.java b/src/main/java/algorithms/sprint2/Deque.java
index c3f3141..2ff7dc2 100644
--- a/src/main/java/algorithms/sprint2/Deque.java
+++ b/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 = safeCapacity(cap);
+            this.a = new int[this.cap];
         }
 
         private int next(int i) {
@@ -110,6 +112,13 @@ int popBack() {
         }
     }
 
+    private static int safeCapacity(int cap) {
+        if (cap < 0) {
+            return 0;
+        }
+        return Math.min(cap, MAX_CAPACITY);
+    }
+
     private static void process(FastIn in, FastOut out) throws Exception {
         int n = in.nextInt();
         int m = in.nextInt();
@@ -233,6 +242,27 @@ private static void test() throws Exception {
                 )
         );
 
+        // Некорректная емкость из ввода не должна приводить к аварийному завершению
+        assertEq(
+                "error\nerror\n",
+                solveIO(
+                        "2\n" +
+                                "-1\n" +
+                                "push_back 1\n" +
+                                "pop_front\n"
+                )
+        );
+
+        // Слишком большая емкость ограничивается безопасным максимумом до выделения массива
+        assertEq(
+                "error\n",
+                solveIO(
+                        "1\n" +
+                                "1000000000\n" +
+                                "pop_front\n"
+                )
+        );
+
         // Wrap-around: head/tail должны корректно "перепрыгивать" границу массива
         assertEq(
                 "1\n4\n2\n3\n",