leetcode

Author: ayoubzulfiqar

PowerOfThree/power_of_three.dart

@@ -0,0 +1,119 @@
+/*
+
+-* 326. Power of Three *-
+
+
+Given an integer n, return true if it is a power of three. Otherwise, return false.
+
+An integer n is a power of three, if there exists an integer x such that n == 3x.
+
+
+
+Example 1:
+
+Input: n = 27
+Output: true
+Explanation: 27 = 33
+Example 2:
+
+Input: n = 0
+Output: false
+Explanation: There is no x where 3x = 0.
+Example 3:
+
+Input: n = -1
+Output: false
+Explanation: There is no x where 3x = (-1).
+
+
+Constraints:
+
+-231 <= n <= 231 - 1
+
+
+Follow up: Could you solve it without loops/recursion?
+
+
+*/
+
+import 'dart:collection';
+import 'dart:math';
+
+class A {
+  bool isPowerOfThree(int n) {
+    if (n <= 0) return false;
+    while (n % 3 == 0) {
+      n ~/= 3;
+    }
+    return n == 1;
+  }
+}
+
+class B {
+  bool isPowerOfThree(int n) {
+    return (log(n) / log(3)) % 1 == 0;
+  }
+}
+
+class C {
+  bool isPowerOfThree(int n) {
+    HashMap<int, bool> m = HashMap();
+    m[1] = true;
+    m[3] = true;
+    m[9] = true;
+    m[27] = true;
+    m[81] = true;
+    m[243] = true;
+    m[729] = true;
+    m[2187] = true;
+    m[6561] = true;
+    m[19683] = true;
+    m[59049] = true;
+    m[177147] = true;
+    m[531441] = true;
+    m[1594323] = true;
+    m[4782969] = true;
+    m[14348907] = true;
+    m[43046721] = true;
+    m[129140163] = true;
+    m[387420489] = true;
+    m[1162261467] = true;
+    return m[n] ?? false;
+  }
+}
+
+class D {
+  bool isPowerOfThree(int n) {
+    if (n <= 1) return n == 1;
+    return n % 3 == 0 && isPowerOfThree(n ~/ 3);
+  }
+}
+
+class E {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    for (; n != 1; n ~/= 3) if (n % 3 != 0) return false;
+    return true;
+  }
+}
+
+class F {
+  bool isPowerOfThree(int n) {
+    return n > 0 && 1162261467 % n == 0;
+    // pow(3, floor(log(INT_MAX)/log(3))) = 1162261467
+  }
+}
+
+class G {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    String nBase3 = "";
+    while (n != 0) nBase3 += (n % 3).toString();
+    n ~/= 3; // conversion to base 3
+    int i = 0;
+    while (i < nBase3.length - 1)
+      if (nBase3[i++] != '0')
+        return false; // checking if all digits in base 3 converted number except first one are 0
+    return nBase3[i] == '1'; // check if starting digit is 1
+  }
+}

PowerOfThree/power_of_three.go

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+package main
+
+func isPowerOfThree(n int) bool {
+	if n <= 0 {
+		return false
+	}
+	for n%3 == 0 {
+		n /= 3
+	}
+	return n == 1
+}

PowerOfThree/power_of_three.md

@@ -0,0 +1,110 @@
+# 🔥 Power of Three 🔥 || 7 Approaches || Simple Fast and Easy || with Explanation
+
+## Solution - 1
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    if (n <= 0) return false;
+    while (n % 3 == 0) {
+      n ~/= 3;
+    }
+    return n == 1;
+  }
+}
+```
+
+## Solution - 2
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    return (log(n) / log(3)) % 1 == 0;
+  }
+}
+```
+
+## Solution - 3
+
+```dart
+import 'dart:collection';
+
+class Solution {
+  bool isPowerOfThree(int n) {
+    HashMap<int, bool> m = HashMap();
+    m[1] = true;
+    m[3] = true;
+    m[9] = true;
+    m[27] = true;
+    m[81] = true;
+    m[243] = true;
+    m[729] = true;
+    m[2187] = true;
+    m[6561] = true;
+    m[19683] = true;
+    m[59049] = true;
+    m[177147] = true;
+    m[531441] = true;
+    m[1594323] = true;
+    m[4782969] = true;
+    m[14348907] = true;
+    m[43046721] = true;
+    m[129140163] = true;
+    m[387420489] = true;
+    m[1162261467] = true;
+    return m[n] ?? false;
+  }
+}
+```
+
+## Solution - 4
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    if (n <= 1) return n == 1;
+    return n % 3 == 0 && isPowerOfThree(n ~/ 3);
+  }
+}
+```
+
+## Solution - 5
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    for (; n != 1; n ~/= 3) if (n % 3 != 0) return false;
+    return true;
+  }
+}
+```
+
+## Solution - 6
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    return n > 0 && 1162261467 % n == 0;
+    // pow(3, floor(log(INT_MAX)/log(3))) = 1162261467
+  }
+}
+```
+
+## Solution - 7
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    String nBase3 = "";
+    while (n != 0) nBase3 += (n % 3).toString();
+    n ~/= 3; // conversion to base 3
+    int i = 0;
+    while (i < nBase3.length - 1)
+      if (nBase3[i++] != '0')
+        return false; // checking if all digits in base 3 converted number except first one are 0
+    return nBase3[i] == '1'; // check if starting digit is 1
+  }
+}
+```

README.md

@@ -127,6 +127,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [**151.** Reverse Words in a String](ReverseWordsInAString/reverse_words_in_a_string.dart)
 - [**947.** Most Stones Removed with Same Row or Column](MostStonesRemovedWithSameRowOrColumn/most_stones_removed_with_same_row_or_column.dart)
 - [**222.** Count Complete Tree Nodes](CountCompleteTreeNodes/count_complete_tree_nodes.dart)
+- [**326.** Power of Three](PowerOfThree/power_of_three.dart)
 
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