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54 lines
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54 lines
2.1 KiB
HTML
<p>You are given a <strong>0-indexed</strong> string <code>s</code> of <strong>even</strong> length <code>n</code>. The string consists of <strong>exactly</strong> <code>n / 2</code> opening brackets <code>'['</code> and <code>n / 2</code> closing brackets <code>']'</code>.</p>
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<p>A string is called <strong>balanced</strong> if and only if:</p>
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<ul>
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<li>It is the empty string, or</li>
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<li>It can be written as <code>AB</code>, where both <code>A</code> and <code>B</code> are <strong>balanced</strong> strings, or</li>
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<li>It can be written as <code>[C]</code>, where <code>C</code> is a <strong>balanced</strong> string.</li>
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</ul>
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<p>You may swap the brackets at <strong>any</strong> two indices <strong>any</strong> number of times.</p>
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<p>Return <em>the <strong>minimum</strong> number of swaps to make </em><code>s</code> <em><strong>balanced</strong></em>.</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> s = "][]["
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<strong>Output:</strong> 1
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<strong>Explanation:</strong> You can make the string balanced by swapping index 0 with index 3.
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The resulting string is "[[]]".
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> s = "]]][[["
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<strong>Output:</strong> 2
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<strong>Explanation:</strong> You can do the following to make the string balanced:
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- Swap index 0 with index 4. s = "[]][][".
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- Swap index 1 with index 5. s = "[[][]]".
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The resulting string is "[[][]]".
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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> s = "[]"
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<strong>Output:</strong> 0
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<strong>Explanation:</strong> The string is already balanced.
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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>n == s.length</code></li>
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<li><code>2 <= n <= 10<sup>6</sup></code></li>
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<li><code>n</code> is even.</li>
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<li><code>s[i]</code> is either <code>'[' </code>or <code>']'</code>.</li>
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<li>The number of opening brackets <code>'['</code> equals <code>n / 2</code>, and the number of closing brackets <code>']'</code> equals <code>n / 2</code>.</li>
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</ul>
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