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Commit e3f3f65

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[3226] Number of Bit Changes to Make Two Integers Equal (#97)
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/*
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3226. Number of Bit Changes to Make Two Integers Equal
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https://leetcode.com/problems/number-of-bit-changes-to-make-two-integers-equal/description/
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You are given two positive integers n and k.
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You can choose any bit in the binary representation of n that is equal to 1 and change it to 0.
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Return the number of changes needed to make n equal to k. If it is impossible, return -1.
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Example 1:
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Input: n = 13, k = 4
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Output: 2
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Explanation:
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Initially, the binary representations of n and k are n = (1101)base2 and k = (0100)base2.
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We can change the first and fourth bits of n. The resulting integer is n = (0100)base2 = k.
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Example 2:
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Input: n = 21, k = 21
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Output: 0
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Explanation:
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n and k are already equal, so no changes are needed.
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Example 3:
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Input: n = 14, k = 13
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Output: -1
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Explanation:
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It is not possible to make n equal to k.
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Constraints:
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1 <= n, k <= 10^6
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*/
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/*
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Approach
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Check if transformation is possible:
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Use a bitwise AND operation to ensure all 1 bits in k are also 1 bits in n. If not, return -1.
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Calculate the number of changes:
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Use a bitwise XOR operation to identify differing bits between n and k.
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Count the number of 1s in the result of the XOR operation.
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*/
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/**
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* @param {number} n
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* @param {number} k
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* @return {number}
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*/
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var minChanges = function bitChanges(n, k) {
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// Check if transformation is possible
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if ((n & k) !== k) {
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return -1;
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}
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// Calculate the number of changes
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let changes = 0;
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let diff = n ^ k;
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while (diff > 0) {
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changes += diff & 1;
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diff >>= 1;
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}
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return changes;
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};
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module.exports.minChanges = minChanges;
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const assert = require("assert");
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const bitReverseToMakeNumberEqual = require("../../../LeetcodeProblems/Algorithms/easy/Bit_Reverse_To_Make_Numbers_Equal").bitChanges;
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function test() {
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assert.deepEqual(
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bitChanges(13, 4),
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2
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);
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assert.deepEqual(
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bitChanges(21, 21),
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0
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);
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assert.deepEqual(
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bitChanges(14, 13),
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-1
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);
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}
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module.exports.test = test;

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