Leetcode problem 3226

LeetcodeProblems/Algorithms/easy/Bit_Reverse_To_Make_Numbers_Equal.js

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+/*
+3226. Number of Bit Changes to Make Two Integers Equal
+https://leetcode.com/problems/number-of-bit-changes-to-make-two-integers-equal/description/
+
+You are given two positive integers n and k.
+
+You can choose any bit in the binary representation of n that is equal to 1 and change it to 0.
+
+Return the number of changes needed to make n equal to k. If it is impossible, return -1.
+
+Example 1:
+
+Input: n = 13, k = 4
+
+Output: 2
+
+Explanation:
+Initially, the binary representations of n and k are n = (1101)base2 and k = (0100)base2.
+We can change the first and fourth bits of n. The resulting integer is n = (0100)base2 = k.
+
+
+Example 2:
+
+Input: n = 21, k = 21
+
+Output: 0
+
+Explanation:
+n and k are already equal, so no changes are needed.
+
+Example 3:
+
+Input: n = 14, k = 13
+
+Output: -1
+
+Explanation:
+It is not possible to make n equal to k.
+
+Constraints:
+
+1 <= n, k <= 10^6
+
+*/
+
+/*
+Approach
+Check if transformation is possible:
+
+Use a bitwise AND operation to ensure all 1 bits in k are also 1 bits in n. If not, return -1.
+Calculate the number of changes:
+
+Use a bitwise XOR operation to identify differing bits between n and k.
+Count the number of 1s in the result of the XOR operation.
+*/
+
+/**
+ * @param {number} n
+ * @param {number} k
+ * @return {number}
+ */
+var minChanges = function bitChanges(n, k) {
+    // Check if transformation is possible
+    if ((n & k) !== k) {
+        return -1;
+    }
+
+    // Calculate the number of changes
+    let changes = 0;
+    let diff = n ^ k;
+
+    while (diff > 0) {
+        changes += diff & 1;
+        diff >>= 1;
+    }
+
+    return changes;
+}

LeetcodeProblemsTests/Algorithms/easy/Bit_Reverse_To_Make_Numbers_Equal.js

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+const assert = require("assert");
+const bitReverseToMakeNumberEqual = require("../../../LeetcodeProblems/Algorithms/easy/Bit_Reverse_To_Make_Numbers_Equal").bitChanges;
+
+
+function test() {
+  assert.deepEqual(
+    bitChanges(13, 4),
+    2
+  );
+  assert.deepEqual(
+    bitChanges(21, 21),
+    0
+  );
+  assert.deepEqual(
+  bitChanges(14, 13),
+  -1
+);
+}
+
+module.exports.test = test;