add 478

fishercoder1534 · fishercoder1534 · commit ae68f30c9d25 · 2021-03-17T08:15:35.000-07:00
diff --git a/README.md b/README.md
@@ -681,6 +681,7 @@ _If you like this project, please leave me a star._ &#9733;
 |480|[Sliding Window Median](https://leetcode.com/problems/sliding-window-median/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_480.java) |  |Hard| Heap
 |479|[Largest Palindrome Product](https://leetcode.com/problems/largest-palindrome-product/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_479.java) |  |Easy| 
 |477|[Total Hamming Distance](https://leetcode.com/problems/total-hamming-distance/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_477.java) |  |Medium| Bit Manipulation
+|478|[Generate Random Point in a Circle](https://leetcode.com/problems/generate-random-point-in-a-circle/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_478.java) | | Medium| Math, Random, Rejection Sampling
 |476|[Number Complement](https://leetcode.com/problems/number-complement/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_476.java) | | Easy| Bit Manipulation
 |475|[Heaters](https://leetcode.com/problems/heaters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_475.java) | |Easy | Array Binary Search
 |474|[Ones and Zeroes](https://leetcode.com/problems/ones-and-zeroes/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_474.java) |  |Medium| DP
diff --git a/src/main/java/com/fishercoder/solutions/_478.java b/src/main/java/com/fishercoder/solutions/_478.java
@@ -0,0 +1,61 @@
+package com.fishercoder.solutions;
+
+public class _478 {
+    public static class Solution1 {
+        /**
+         * credit: https://leetcode.com/problems/generate-random-point-in-a-circle/discuss/154037/Polar-Coordinates-10-lines
+         * and
+         * https://leetcode.com/problems/generate-random-point-in-a-circle/discuss/155650/Explanation-with-Graphs-why-using-Math.sqrt()
+         */
+        double radius, xCenter, yCenter;
+
+        public Solution1(double radius, double xCenter, double yCenter) {
+            this.radius = radius;
+            this.xCenter = xCenter;
+            this.yCenter = yCenter;
+        }
+
+        public double[] randPoint() {
+            double len = Math.sqrt(Math.random()) * radius;
+            double degree = Math.random() * 2 * Math.PI;
+            double x = xCenter + len * Math.cos(degree);
+            double y = yCenter + len * Math.sin(degree);
+            return new double[]{x, y};
+        }
+    }
+
+    public static class Solution2 {
+        /**
+         * How to know one point is within a circle:
+         * https://www.geeksforgeeks.org/find-if-a-point-lies-inside-or-on-circle/
+         */
+        double top;
+        double bottom;
+        double left;
+        double right;
+        double rad;
+        double xCenter;
+        double yCenter;
+
+        public Solution2(double radius, double xCenter, double yCenter) {
+            this.rad = radius;
+            this.top = yCenter + radius;
+            this.bottom = yCenter - radius;
+            this.left = xCenter - radius;
+            this.right = xCenter + radius;
+            this.xCenter = xCenter;
+            this.yCenter = yCenter;
+        }
+
+        public double[] randPoint() {
+            double[] result = new double[2];
+            result[0] = (Math.random() * (right - left)) + left;
+            result[1] = (Math.random() * (top - bottom)) + bottom;
+            while (Math.pow(result[0] - xCenter, 2.0) + Math.pow(result[1] - yCenter, 2.0) > Math.pow(rad, 2.0)) {
+                result[0] = (Math.random() * (right - left)) + left;
+                result[1] = (Math.random() * (top - bottom)) + bottom;
+            }
+            return result;
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_478Test.java b/src/test/java/com/fishercoder/_478Test.java
@@ -0,0 +1,16 @@
+package com.fishercoder;
+
+import com.fishercoder.common.utils.CommonUtils;
+import com.fishercoder.solutions._478;
+import org.junit.Test;
+
+public class _478Test {
+    private static _478.Solution1 solution1;
+
+    @Test
+    public void test1() {
+        solution1 = new _478.Solution1(10.0, 5.0, -7.5);
+        CommonUtils.printArray(solution1.randPoint());
+    }
+
+}
