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39 lines
2.0 KiB
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<p>A <strong>bit flip</strong> of a number <code>x</code> is choosing a bit in the binary representation of <code>x</code> and <strong>flipping</strong> it from either <code>0</code> to <code>1</code> or <code>1</code> to <code>0</code>.</p>
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<ul>
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<li>For example, for <code>x = 7</code>, the binary representation is <code>111</code> and we may choose any bit (including any leading zeros not shown) and flip it. We can flip the first bit from the right to get <code>110</code>, flip the second bit from the right to get <code>101</code>, flip the fifth bit from the right (a leading zero) to get <code>10111</code>, etc.</li>
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</ul>
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<p>Given two integers <code>start</code> and <code>goal</code>, return<em> the <strong>minimum</strong> number of <strong>bit flips</strong> to convert </em><code>start</code><em> to </em><code>goal</code>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> start = 10, goal = 7
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<strong>Output:</strong> 3
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<strong>Explanation:</strong> The binary representation of 10 and 7 are 1010 and 0111 respectively. We can convert 10 to 7 in 3 steps:
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- Flip the first bit from the right: 101<u>0</u> -> 101<u>1</u>.
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- Flip the third bit from the right: 1<u>0</u>11 -> 1<u>1</u>11.
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- Flip the fourth bit from the right: <u>1</u>111 -> <u>0</u>111.
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It can be shown we cannot convert 10 to 7 in less than 3 steps. Hence, we return 3.</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> start = 3, goal = 4
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<strong>Output:</strong> 3
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<strong>Explanation:</strong> The binary representation of 3 and 4 are 011 and 100 respectively. We can convert 3 to 4 in 3 steps:
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- Flip the first bit from the right: 01<u>1</u> -> 01<u>0</u>.
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- Flip the second bit from the right: 0<u>1</u>0 -> 0<u>0</u>0.
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- Flip the third bit from the right: <u>0</u>00 -> <u>1</u>00.
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It can be shown we cannot convert 3 to 4 in less than 3 steps. Hence, we return 3.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>0 <= start, goal <= 10<sup>9</sup></code></li>
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</ul>
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