feat: solve No.2610,478

Author: BaffinLee

2601-2700/2610. Convert an Array Into a 2D Array With Conditions.md

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+# 2610. Convert an Array Into a 2D Array With Conditions
+
+- Difficulty: Medium.
+- Related Topics: Array, Hash Table.
+- Similar Questions: .
+
+## Problem
+
+You are given an integer array `nums`. You need to create a 2D array from `nums` satisfying the following conditions:
+
+
+	
+- The 2D array should contain **only** the elements of the array `nums`.
+	
+- Each row in the 2D array contains **distinct** integers.
+	
+- The number of rows in the 2D array should be **minimal**.
+
+
+Return **the resulting array**. If there are multiple answers, return any of them.
+
+**Note** that the 2D array can have a different number of elements on each row.
+
+ 
+Example 1:
+
+```
+Input: nums = [1,3,4,1,2,3,1]
+Output: [[1,3,4,2],[1,3],[1]]
+Explanation: We can create a 2D array that contains the following rows:
+- 1,3,4,2
+- 1,3
+- 1
+All elements of nums were used, and each row of the 2D array contains distinct integers, so it is a valid answer.
+It can be shown that we cannot have less than 3 rows in a valid array.
+```
+
+Example 2:
+
+```
+Input: nums = [1,2,3,4]
+Output: [[4,3,2,1]]
+Explanation: All elements of the array are distinct, so we can keep all of them in the first row of the 2D array.
+```
+
+ 
+**Constraints:**
+
+
+	
+- `1 <= nums.length <= 200`
+	
+- `1 <= nums[i] <= nums.length`
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var findMatrix = function(nums) {
+    var numMap = Array(nums.length + 1).fill(0);
+    var res = [];
+    for (var i = 0; i < nums.length; i++) {
+        var num = nums[i];
+        var row = numMap[nums[i]];
+        if (!res[row]) {
+            res.push([]);
+        }
+        res[row].push(num);
+        numMap[num]++;
+    }
+    return res;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).

401-500/478. Generate Random Point in a Circle.md

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+# 478. Generate Random Point in a Circle
+
+- Difficulty: Medium.
+- Related Topics: Math, Geometry, Rejection Sampling, Randomized.
+- Similar Questions: Random Point in Non-overlapping Rectangles.
+
+## Problem
+
+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:**
+
+
+	
+- `0 < radius <= 108`
+	
+- `-107 <= x_center, y_center <= 107`
+	
+- At most `3 * 104` calls will be made to `randPoint`.
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number} radius
+ * @param {number} x_center
+ * @param {number} y_center
+ */
+var Solution = function(radius, x_center, y_center) {
+    this.radius = radius;
+    this.centerX = x_center;
+    this.centerY = y_center;
+};
+
+/**
+ * @return {number[]}
+ */
+Solution.prototype.randPoint = function() {
+    var radius = Math.sqrt(Math.random()) * this.radius;
+    var rand = Math.random();
+    var degree = Math.PI / 2 * (rand === 1 ? 0 : rand);
+    var x = Math.cos(degree) * radius;
+    var y = Math.sin(degree) * radius;
+    return [
+        this.centerX + (Math.random() > 0.5 ? 1 : -1) * x,
+        this.centerY + (Math.random() > 0.5 ? 1 : -1) * y,
+    ];
+};
+
+/** 
+ * Your Solution object will be instantiated and called as such:
+ * var obj = new Solution(radius, x_center, y_center)
+ * var param_1 = obj.randPoint()
+ */
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).