leetcode

Author: ayoubzulfiqar

PowerOfFour/power_of_four.dart

@@ -0,0 +1,73 @@
+/*
+
+ -* 342. Power of Four *-
+
+ Given an integer n, return true if it is a power of four. Otherwise, return false.
+
+An integer n is a power of four, if there exists an integer x such that n == 4x.
+
+
+
+Example 1:
+
+Input: n = 16
+Output: true
+Example 2:
+
+Input: n = 5
+Output: false
+Example 3:
+
+Input: n = 1
+Output: true
+
+
+Constraints:
+
+-231 <= n <= 231 - 1
+
+
+Follow up: Could you solve it without loops/recursion?
+
+
+
+*/
+
+import 'dart:math';
+
+class A {
+  bool isPowerOfFour(int n) {
+    if (n <= 0) return false;
+    while (n % 3 == 0) {
+      n ~/= 3;
+    }
+    return n == 1;
+  }
+}
+
+class B {
+  bool isPowerOfFour(int n) {
+    return (log(n) / log(4)) % 1 == 0;
+  }
+}
+
+class C {
+  bool isPowerOfFour(int n) {
+    if (n <= 1) return n == 1;
+    return n % 4 == 0 && isPowerOfFour(n ~/ 4);
+  }
+}
+
+class D {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    String nBase4 = "";
+    while (n != 0) nBase4 += (n % 4).toString();
+    n ~/= 3; // conversion to base 3
+    int i = 0;
+    while (i < nBase4.length - 1)
+      if (nBase4[i++] != '0')
+        return false; // checking if all digits in base 3 converted number except first one are 0
+    return nBase4[i] == '1'; // check if starting digit is 1
+  }
+}

PowerOfFour/power_of_four.go

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+package main
+
+func isPowerOfFour(n int) bool {
+	if n <= 0 {
+		return false
+	}
+
+	for n%4 == 0 {
+		n /= 4
+	}
+	return n == 1
+}

PowerOfFour/power_of_four.md

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+# 🔥 Power of Four 🔥 || 4  Approaches || Simple Fast and Easy || with Explanation
+
+## Solution - 1
+
+```dart
+class Solution {
+  bool isPowerOfFour(int n) {
+    if (n <= 0) return false;
+    while (n % 3 == 0) {
+      n ~/= 3;
+    }
+    return n == 1;
+  }
+}
+```
+
+## Solution - 2
+
+```dart
+class Solution {
+  bool isPowerOfFour(int n) {
+    if (n <= 1) return n == 1;
+    return n % 4 == 0 && isPowerOfFour(n ~/ 4);
+  }
+}
+```
+
+## Solution - 3
+
+```dart
+class Solution {
+  bool isPowerOfFour(int n) {
+    return (log(n) / log(4)) % 1 == 0;
+  }
+}
+```
+
+## Solution - 4
+
+```dart
+class Solution {
+  bool isPowerOfThree(int n) {
+    if (n < 1) return false;
+    String nBase4 = "";
+    while (n != 0) nBase4 += (n % 4).toString();
+    n ~/= 3; // conversion to base 3
+    int i = 0;
+    while (i < nBase4.length - 1)
+      if (nBase4[i++] != '0')
+        return false; // checking if all digits in base 3 converted number except first one are 0
+    return nBase4[i] == '1'; // check if starting digit is 1
+  }
+}
+```

README.md

@@ -130,6 +130,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [**326.** Power of Three](PowerOfThree/power_of_three.dart)
 - [**338.** Counting Bits](CountingBits/counting_bits.dart)
 - [**374.** Guess Number Higher or Lower](GuessNumberHigherOrLower/guess_number_higher_or_lower.dart)
+- [**342.** Power of Four](PowerOfFour/power_of_four.dart)
 
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