9808Tarun · Nov 11, 2026 · Nov 11, 2026
diff --git a/Maths/test/ParityOutlier.test.js b/Maths/test/ParityOutlier.test.js
@@ -23,3 +23,60 @@ describe('Testing parityOutlier function', () => {
     expect(parityOutlier([1, 3, 5, 7, 2, 4, 6, 8])).toBe(null)
   })
 })
+
+describe('parityOutlier contract & invariant checks (Precondition near line 9 of Maths/ParityOutlier.js)', () => {
+  test('Smallest valid input ([1, 2])', () => {
+    const input = [1, 2]
+    expect(parityOutlier(input)).toBe(1)
+  })
+
+  test('Ordinary input ([1, 2, 16, -8848, 5126])', () => {
+    const input = [1, 2, 16, -8848, 5126]
+    expect(parityOutlier(input)).toBe(1)
+  })
+
+  test('Preserves input array immutability', () => {
+    const input = [1, 2, 16, -8848, 5126]
+    const copy = [...input]
+    parityOutlier(input)
+    expect(input).toEqual(copy)
+  })
+
+  // Seeded LCG generator for 100 bounded valid property cases
+  function createLCG(seed = 12345) {
+    let state = seed
+    return function () {
+      state = (state * 1664525 + 1013904223) % 4294967296
+      return state / 4294967296
+    }
+  }
+
+  test('Property test: 100 generated bounded valid inputs satisfy parity outlier invariant', () => {
+    const rand = createLCG(42)
+
+    for (let i = 0; i < 100; i++) {
+      const isOutlierOdd = rand() > 0.5
+      const length = 3 + Math.floor(rand() * 20)
+      const outlierIndex = Math.floor(rand() * length)
+
+      const arr = []
+      for (let j = 0; j < length; j++) {
+        if (j === outlierIndex) {
+          const val = Math.floor(rand() * 1000) * 2 + (isOutlierOdd ? 1 : 0)
+          arr.push(val)
+        } else {
+          const val = Math.floor(rand() * 1000) * 2 + (isOutlierOdd ? 0 : 1)
+          arr.push(val)
+        }
+      }
+
+      const expectedOutlier = arr[outlierIndex]
+      const actualOutlier = parityOutlier(arr)
+
+      expect(actualOutlier).toBe(expectedOutlier)
+      const actualParity = Math.abs(actualOutlier % 2)
+      const expectedParity = isOutlierOdd ? 1 : 0
+      expect(actualParity).toBe(expectedParity)
+    }
+  })
+})
diff --git a/work/R50-T024/check.py b/work/R50-T024/check.py
@@ -0,0 +1,41 @@
+import os
+import subprocess
+import json
+import sys
+
+def run_checks():
+    work_dir = "work/R50-T024"
+    os.makedirs(work_dir, exist_ok=True)
+
+    node_ver = subprocess.check_output(["node", "-v"]).decode().strip()
+    npm_ver = subprocess.check_output(["npm", "-v"]).decode().strip()
+    with open(f"{work_dir}/versions.json", "w") as f:
+        json.dump({"node": node_ver, "npm": npm_ver}, f, indent=2)
+
+    cmd = ["npx", "vitest", "run", "Maths/test/ParityOutlier.test.js"]
+    res = subprocess.run(cmd, capture_output=True, text=True)
+
+    if res.returncode != 0:
+        cmd = ["npx", "vitest", "run", "Maths/tests/ParityOutlier.test.js"]
+        res = subprocess.run(cmd, capture_output=True, text=True)
+
+    with open(f"{work_dir}/test_output.log", "w") as f:
+        f.write(res.stdout + "\n" + res.stderr)
+
+    if res.returncode == 0:
+        with open(f"{work_dir}/fixture_results.json", "w") as f:
+            json.dump({
+                "status": "PASSED",
+                "task": "R50-T024",
+                "precondition_line": "Maths/ParityOutlier.js:9",
+                "smallest_valid_input": {"input": [1, 2], "expected": 1},
+                "ordinary_input": {"input": [1, 2, 16, -8848, 5126], "expected": 1},
+                "property_tests_run": 100
+            }, f, indent=2)
+        print("All checks passed.")
+    else:
+        print("Tests failed!")
+        sys.exit(1)
+
+if __name__ == "__main__":
+    run_checks()
diff --git a/work/R50-T024/fixture_results.json b/work/R50-T024/fixture_results.json
@@ -0,0 +1,23 @@
+{
+  "status": "PASSED",
+  "task": "R50-T024",
+  "precondition_line": "Maths/ParityOutlier.js:9",
+  "smallest_valid_input": {
+    "input": [
+      1,
+      2
+    ],
+    "expected": 1
+  },
+  "ordinary_input": {
+    "input": [
+      1,
+      2,
+      16,
+      -8848,
+      5126
+    ],
+    "expected": 1
+  },
+  "property_tests_run": 100
+}
diff --git a/work/R50-T024/test_output.log b/work/R50-T024/test_output.log
@@ -0,0 +1,11 @@
+
+[1m[30m[46m RUN [49m[39m[22m [36mv5.1.0 [39m[90m/Users/fabulous_tarun8/Library/Mobile Documents/com~apple~CloudDocs/Studies/s&ai/diwaliHomework/TheAlgorithms-JavaScript[39m
+
+ [32m✓[39m Maths/test/ParityOutlier.test.js [2m([22m[2m8 tests[22m[2m)[22m[32m 3[2mms[22m[39m
+
+[2m Test Files [22m [1m[32m1 passed[39m[22m[90m (1)[39m
+[2m      Tests [22m [1m[32m8 passed[39m[22m[90m (8)[39m
+[2m   Start at [22m 08:46:44
+[2m   Duration [22m 78ms[2m (import 28%, worker 26%, tests 25%, transform 22%, environment 1%)[22m
+
+
diff --git a/work/R50-T024/versions.json b/work/R50-T024/versions.json
@@ -0,0 +1,4 @@
+{
+  "node": "v26.12.1",
+  "npm": "11.20.0"
+}