Added tasks 477, 478, 479, 480.

src/main/kotlin/g0401_0500/s0477_total_hamming_distance/Solution.kt

@@ -0,0 +1,18 @@
+package g0401_0500.s0477_total_hamming_distance
+
+// #Medium #Array #Math #Bit_Manipulation #2023_01_01_Time_298_ms_(100.00%)_Space_38.6_MB_(100.00%)
+
+class Solution {
+    fun totalHammingDistance(nums: IntArray): Int {
+        var ans = 0
+        val n = nums.size
+        for (i in 0..31) {
+            var ones = 0
+            for (k in nums) {
+                ones += k shr i and 1
+            }
+            ans = ans + ones * (n - ones)
+        }
+        return ans
+    }
+}

src/main/kotlin/g0401_0500/s0477_total_hamming_distance/readme.md

@@ -0,0 +1,31 @@
+477\. Total Hamming Distance
+
+Medium
+
+The [Hamming distance](https://en.wikipedia.org/wiki/Hamming_distance) between two integers is the number of positions at which the corresponding bits are different.
+
+Given an integer array `nums`, return _the sum of **Hamming distances** between all the pairs of the integers in_ `nums`.
+
+**Example 1:**
+
+**Input:** nums = [4,14,2]
+
+**Output:** 6
+
+**Explanation:** In binary representation, the 4 is 0100, 14 is 1110, and 2 is 0010 (just showing the four bits relevant in this case). 
+
+The answer will be: 
+
+HammingDistance(4, 14) + HammingDistance(4, 2) + HammingDistance(14, 2) = 2 + 2 + 2 = 6.
+
+**Example 2:**
+
+**Input:** nums = [4,14,4]
+
+**Output:** 4
+
+**Constraints:**
+
+*   <code>1 <= nums.length <= 10<sup>4</sup></code>
+*   <code>0 <= nums[i] <= 10<sup>9</sup></code>
+*   The answer for the given input will fit in a **32-bit** integer.

src/main/kotlin/g0401_0500/s0478_generate_random_point_in_a_circle/Solution.kt

@@ -0,0 +1,34 @@
+package g0401_0500.s0478_generate_random_point_in_a_circle
+
+// #Medium #Math #Geometry #Randomized #Rejection_Sampling
+// #2023_01_01_Time_862_ms_(100.00%)_Space_70_MB_(66.67%)
+
+import java.util.Random
+
+@Suppress("kotlin:S2245")
+class Solution(private val radius: Double, private val xCenter: Double, private val yCenter: Double) {
+    private val random: Random = Random()
+    fun randPoint(): DoubleArray {
+        var x = getCoordinate(xCenter)
+        var y = getCoordinate(yCenter)
+        while (getDistance(x, y) >= radius * radius) {
+            x = getCoordinate(xCenter)
+            y = getCoordinate(yCenter)
+        }
+        return doubleArrayOf(x, y)
+    }
+
+    private fun getDistance(x: Double, y: Double): Double {
+        return (xCenter - x) * (xCenter - x) + (yCenter - y) * (yCenter - y)
+    }
+
+    private fun getCoordinate(center: Double): Double {
+        return center - radius + random.nextDouble() * 2 * radius
+    }
+}
+
+/*
+ * Your Solution object will be instantiated and called as such:
+ * var obj = Solution(radius, x_center, y_center)
+ * var param_1 = obj.randPoint()
+ */

src/main/kotlin/g0401_0500/s0478_generate_random_point_in_a_circle/readme.md

@@ -0,0 +1,29 @@
+478\. Generate Random Point in a Circle
+
+Medium
+
+Given the radius and the position of the center of a circle, implement the function `randPoint` which generates a uniform random point inside the circle.
+
+Implement the `Solution` class:
+
+*   `Solution(double radius, double x_center, double y_center)` initializes the object with the radius of the circle `radius` and the position of the center `(x_center, y_center)`.
+*   `randPoint()` returns a random point inside the circle. A point on the circumference of the circle is considered to be in the circle. The answer is returned as an array `[x, y]`.
+
+**Example 1:**
+
+**Input** ["Solution", "randPoint", "randPoint", "randPoint"] [[1.0, 0.0, 0.0], [], [], []]
+
+**Output:** [null, [-0.02493, -0.38077], [0.82314, 0.38945], [0.36572, 0.17248]]
+
+**Explanation:** 
+
+    Solution solution = new Solution(1.0, 0.0, 0.0); 
+    solution.randPoint(); // return [-0.02493, -0.38077] 
+    solution.randPoint(); // return [0.82314, 0.38945] 
+    solution.randPoint(); // return [0.36572, 0.17248]
+
+**Constraints:**
+
+*   <code>0 < radius <= 10<sup>8</sup></code>
+*   <code>-10<sup>7</sup> <= x_center, y_center <= 10<sup>7</sup></code>
+*   At most <code>3 * 10<sup>4</sup></code> calls will be made to `randPoint`.

src/main/kotlin/g0401_0500/s0479_largest_palindrome_product/Solution.kt

@@ -0,0 +1,35 @@
+package g0401_0500.s0479_largest_palindrome_product
+
+// #Hard #Math #2023_01_01_Time_147_ms_(100.00%)_Space_32.8_MB_(100.00%)
+
+@Suppress("NAME_SHADOWING")
+class Solution {
+    fun largestPalindrome(n: Int): Int {
+        val pow10 = Math.pow(10.0, n.toDouble()).toLong()
+        val max = (pow10 - 1) * (pow10 - Math.sqrt(pow10.toDouble()).toLong() + 1)
+        val left = max / pow10
+        var t = pow10 / 11
+        t -= t.inv() and 1L
+        for (i in left downTo 1) {
+            var j = t
+            val num = gen(i)
+            while (j >= i / 11) {
+                if (num % j == 0L) {
+                    return (num % 1337).toInt()
+                }
+                j -= 2
+            }
+        }
+        return 9
+    }
+
+    private fun gen(x: Long): Long {
+        var x = x
+        var r = x
+        while (x > 0) {
+            r = r * 10 + x % 10
+            x /= 10
+        }
+        return r
+    }
+}

src/main/kotlin/g0401_0500/s0479_largest_palindrome_product/readme.md

@@ -0,0 +1,21 @@
+479\. Largest Palindrome Product
+
+Hard
+
+Given an integer n, return _the **largest palindromic integer** that can be represented as the product of two `n`\-digits integers_. Since the answer can be very large, return it **modulo** `1337`.
+
+**Example 1:**
+
+**Input:** n = 2
+
+**Output:** 987 Explanation: 99 x 91 = 9009, 9009 % 1337 = 987
+
+**Example 2:**
+
+**Input:** n = 1
+
+**Output:** 9
+
+**Constraints:**
+
+*   `1 <= n <= 8`

src/main/kotlin/g0401_0500/s0480_sliding_window_median/Solution.kt

@@ -0,0 +1,64 @@
+package g0401_0500.s0480_sliding_window_median
+
+// #Hard #Array #Hash_Table #Heap_Priority_Queue #Sliding_Window
+// #2023_01_01_Time_409_ms_(100.00%)_Space_44.6_MB_(81.48%)
+
+import java.util.TreeSet
+
+class Solution {
+    fun medianSlidingWindow(nums: IntArray, k: Int): DoubleArray {
+        require(k >= 1) { "Input is invalid" }
+        val len = nums.size
+        val result = DoubleArray(len - k + 1)
+        if (k == 1) {
+            for (i in 0 until len) {
+                result[i] = nums[i].toDouble()
+            }
+            return result
+        }
+        val comparator = Comparator { a: Int?, b: Int? ->
+            if (nums[a!!] != nums[b!!]
+            ) Integer.compare(nums[a], nums[b]) else Integer.compare(a, b)
+        }
+        val smallNums = TreeSet(comparator.reversed())
+        val largeNums = TreeSet(comparator)
+        for (i in 0 until len) {
+            if (i >= k) {
+                removeElement(smallNums, largeNums, i - k)
+            }
+            addElement(smallNums, largeNums, i)
+            if (i >= k - 1) {
+                result[i - (k - 1)] = getMedian(smallNums, largeNums, nums)
+            }
+        }
+        return result
+    }
+
+    private fun addElement(smallNums: TreeSet<Int?>, largeNums: TreeSet<Int?>, idx: Int) {
+        smallNums.add(idx)
+        largeNums.add(smallNums.pollFirst()!!)
+        if (smallNums.size < largeNums.size) {
+            smallNums.add(largeNums.pollFirst())
+        }
+    }
+
+    private fun removeElement(smallNums: TreeSet<Int?>, largeNums: TreeSet<Int?>, idx: Int) {
+        if (largeNums.contains(idx)) {
+            largeNums.remove(idx)
+            if (smallNums.size == largeNums.size + 2) {
+                largeNums.add(smallNums.pollFirst()!!)
+            }
+        } else {
+            smallNums.remove(idx)
+            if (smallNums.size < largeNums.size) {
+                smallNums.add(largeNums.pollFirst())
+            }
+        }
+    }
+
+    private fun getMedian(smallNums: TreeSet<Int?>, largeNums: TreeSet<Int?>, nums: IntArray): Double {
+        return if (smallNums.size == largeNums.size) {
+            (nums[smallNums.first()!!].toDouble() + nums[largeNums.first()!!]) / 2
+        } else nums[smallNums.first()!!].toDouble()
+    }
+}

src/main/kotlin/g0401_0500/s0480_sliding_window_median/readme.md

@@ -0,0 +1,31 @@
+480\. Sliding Window Median
+
+Hard
+
+The **median** is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middle values.
+
+*   For examples, if <code>arr = [2,<ins>3</ins>,4]</code>, the median is `3`.
+*   For examples, if <code>arr = [1,<ins>2,3</ins>,4]</code>, the median is `(2 + 3) / 2 = 2.5`.
+
+You are given an integer array `nums` and an integer `k`. There is a sliding window of size `k` which is moving from the very left of the array to the very right. You can only see the `k` numbers in the window. Each time the sliding window moves right by one position.
+
+Return _the median array for each window in the original array_. Answers within <code>10<sup>-5</sup></code> of the actual value will be accepted.
+
+**Example 1:**
+
+**Input:** nums = [1,3,-1,-3,5,3,6,7], k = 3
+
+**Output:** [1.00000,-1.00000,-1.00000,3.00000,5.00000,6.00000]
+
+**Explanation:** Window position Median --------------- ----- [**1 3 -1**] -3 5 3 6 7 1 1 [**3 -1 -3**] 5 3 6 7 -1 1 3 [**\-1 -3 5**] 3 6 7 -1 1 3 -1 [**\-3 5 3**] 6 7 3 1 3 -1 -3 [**5 3 6**] 7 5 1 3 -1 -3 5 [**3 6 7**] 6
+
+**Example 2:**
+
+**Input:** nums = [1,2,3,4,2,3,1,4,2], k = 3
+
+**Output:** [2.00000,3.00000,3.00000,3.00000,2.00000,3.00000,2.00000]
+
+**Constraints:**
+
+*   <code>1 <= k <= nums.length <= 10<sup>5</sup></code>
+*   <code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code>

src/test/kotlin/g0401_0500/s0477_total_hamming_distance/SolutionTest.kt

@@ -0,0 +1,17 @@
+package g0401_0500.s0477_total_hamming_distance
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun totalHammingDistance() {
+        assertThat(Solution().totalHammingDistance(intArrayOf(4, 14, 2)), equalTo(6))
+    }
+
+    @Test
+    fun totalHammingDistance2() {
+        assertThat(Solution().totalHammingDistance(intArrayOf(4, 14, 4)), equalTo(4))
+    }
+}

src/test/kotlin/g0401_0500/s0478_generate_random_point_in_a_circle/SolutionTest.kt

@@ -0,0 +1,16 @@
+package g0401_0500.s0478_generate_random_point_in_a_circle
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun randPoint() {
+        val solution = Solution(1.0, 0.0, 0.0)
+        solution.randPoint()
+        solution.randPoint()
+        solution.randPoint()
+        assertThat(solution, equalTo(solution))
+    }
+}

src/test/kotlin/g0401_0500/s0479_largest_palindrome_product/SolutionTest.kt

@@ -0,0 +1,17 @@
+package g0401_0500.s0479_largest_palindrome_product
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun largestPalindrome() {
+        assertThat(Solution().largestPalindrome(2), equalTo(987))
+    }
+
+    @Test
+    fun largestPalindrome2() {
+        assertThat(Solution().largestPalindrome(1), equalTo(9))
+    }
+}

src/test/kotlin/g0401_0500/s0480_sliding_window_median/SolutionTest.kt

@@ -0,0 +1,27 @@
+package g0401_0500.s0480_sliding_window_median
+
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.jupiter.api.Test
+
+internal class SolutionTest {
+    @Test
+    fun medianSlidingWindow() {
+        assertThat(
+            Solution().medianSlidingWindow(intArrayOf(1, 3, -1, -3, 5, 3, 6, 7), 3),
+            equalTo(doubleArrayOf(1.00000, -1.00000, -1.00000, 3.00000, 5.00000, 6.00000))
+        )
+    }
+
+    @Test
+    fun medianSlidingWindow2() {
+        assertThat(
+            Solution().medianSlidingWindow(intArrayOf(1, 2, 3, 4, 2, 3, 1, 4, 2), 3),
+            equalTo(
+                doubleArrayOf(
+                    2.00000, 3.00000, 3.00000, 3.00000, 2.00000, 3.00000, 2.00000
+                )
+            )
+        )
+    }
+}