add a solution for 264

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/firstthousand/_264.java

@@ -69,4 +69,21 @@ public int nthUglyNumber(int n) {
             return -1;
         }
     }
+
+    public static class Solution3 {
+
+        public int nthUglyNumber(int n) {
+            TreeSet<Long> treeSet = new TreeSet<>();
+            treeSet.add(1L);
+            int[] arr = new int[]{2, 3, 5};
+            long currentUgly = 0;
+            for (int i = 0; i < n; i++) {
+                currentUgly = treeSet.pollFirst();
+                treeSet.add(currentUgly * arr[0]);
+                treeSet.add(currentUgly * arr[1]);
+                treeSet.add(currentUgly * arr[2]);
+            }
+            return (int) currentUgly;
+        }
+    }
 }

src/test/java/com/fishercoder/firstthousand/_264Test.java

@@ -9,17 +9,20 @@
 public class _264Test {
     private _264.Solution1 solution1;
     private _264.Solution2 solution2;
+    private _264.Solution3 solution3;
 
     @BeforeEach
     public void setup() {
         solution1 = new _264.Solution1();
         solution2 = new _264.Solution2();
+        solution3 = new _264.Solution3();
     }
 
     @Test
     public void test1() {
         assertEquals(12, solution1.nthUglyNumber(10));
         assertEquals(12, solution2.nthUglyNumber(10));
+        assertEquals(12, solution3.nthUglyNumber(10));
     }
 
     @Test