add 1780

fishercoder1534 · fishercoder1534 · commit ec5a38e5bab0 · 2021-03-06T08:29:27.000-08:00
diff --git a/README.md b/README.md
@@ -8,6 +8,7 @@ _If you like this project, please leave me a star._ &#9733;
 
 |  #  |      Title     |   Solutions   | Video  | Difficulty  | Tag                   
 |-----|----------------|---------------|--------|-------------|-------------
+|1780|[Check if Number is a Sum of Powers of Three](https://leetcode.com/problems/check-if-number-is-a-sum-of-powers-of-three/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1780.java) ||Medium|Math, Backtracking, Recursion|
 |1779|[Find Nearest Point That Has the Same X or Y Coordinate](https://leetcode.com/problems/find-nearest-point-that-has-the-same-x-or-y-coordinate/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1779.java) ||Easy|Array|
 |1774|[Closest Dessert Cost](https://leetcode.com/problems/closest-dessert-cost/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1774.java) ||Medium|Greedy|
 |1773|[Count Items Matching a Rule](https://leetcode.com/problems/count-items-matching-a-rule/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1773.java) ||Easy|Array, String|
diff --git a/src/main/java/com/fishercoder/solutions/_1780.java b/src/main/java/com/fishercoder/solutions/_1780.java
@@ -0,0 +1,28 @@
+package com.fishercoder.solutions;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class _1780 {
+    public static class Solution1 {
+        public boolean checkPowersOfThree(int n) {
+            List<Integer> powers = new ArrayList<>();
+            int power = 1;
+            for (int i = 1; power <= n; i++) {
+                powers.add(power);
+                power = (int) Math.pow(3, i);
+            }
+            int i = powers.size() - 1;
+            while (n > 0 && i >= 0) {
+                if (n - powers.get(i) > 0) {
+                    n -= powers.get(i--);
+                } else if (n - powers.get(i) == 0) {
+                    return true;
+                } else {
+                    i--;
+                }
+            }
+            return n == 0;
+        }
+    }
+}
