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70 lines
3.5 KiB
HTML
70 lines
3.5 KiB
HTML
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<p>You are given an integer array <code>nums</code>.</p>
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<p>Start by selecting a starting position <code>curr</code> such that <code>nums[curr] == 0</code>, and choose a movement <strong>direction</strong> of either left or right.</p>
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<p>After that, you repeat the following process:</p>
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<ul>
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<li>If <code>curr</code> is out of the range <code>[0, n - 1]</code>, this process ends.</li>
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<li>If <code>nums[curr] == 0</code>, move in the current direction by <strong>incrementing</strong> <code>curr</code> if you are moving right, or <strong>decrementing</strong> <code>curr</code> if you are moving left.</li>
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<li>Else if <code>nums[curr] > 0</code>:
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<ul>
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<li>Decrement <code>nums[curr]</code> by 1.</li>
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<li><strong>Reverse</strong> your movement direction (left becomes right and vice versa).</li>
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<li>Take a step in your new direction.</li>
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</ul>
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</li>
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</ul>
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<p>A selection of the initial position <code>curr</code> and movement direction is considered <strong>valid</strong> if every element in <code>nums</code> becomes 0 by the end of the process.</p>
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<p>Return the number of possible <strong>valid</strong> selections.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<div class="example-block">
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<p><strong>Input:</strong> <span class="example-io">nums = [1,0,2,0,3]</span></p>
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<p><strong>Output:</strong> <span class="example-io">2</span></p>
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<p><strong>Explanation:</strong></p>
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<p>The only possible valid selections are the following:</p>
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<ul>
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<li>Choose <code>curr = 3</code>, and a movement direction to the left.
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<ul>
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<li><code>[1,0,2,<strong><u>0</u></strong>,3] -> [1,0,<strong><u>2</u></strong>,0,3] -> [1,0,1,<strong><u>0</u></strong>,3] -> [1,0,1,0,<strong><u>3</u></strong>] -> [1,0,1,<strong><u>0</u></strong>,2] -> [1,0,<strong><u>1</u></strong>,0,2] -> [1,0,0,<strong><u>0</u></strong>,2] -> [1,0,0,0,<strong><u>2</u></strong>] -> [1,0,0,<strong><u>0</u></strong>,1] -> [1,0,<strong><u>0</u></strong>,0,1] -> [1,<strong><u>0</u></strong>,0,0,1] -> [<strong><u>1</u></strong>,0,0,0,1] -> [0,<strong><u>0</u></strong>,0,0,1] -> [0,0,<strong><u>0</u></strong>,0,1] -> [0,0,0,<strong><u>0</u></strong>,1] -> [0,0,0,0,<strong><u>1</u></strong>] -> [0,0,0,0,0]</code>.</li>
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</ul>
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</li>
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<li>Choose <code>curr = 3</code>, and a movement direction to the right.
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<ul>
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<li><code>[1,0,2,<strong><u>0</u></strong>,3] -> [1,0,2,0,<strong><u>3</u></strong>] -> [1,0,2,<strong><u>0</u></strong>,2] -> [1,0,<strong><u>2</u></strong>,0,2] -> [1,0,1,<strong><u>0</u></strong>,2] -> [1,0,1,0,<strong><u>2</u></strong>] -> [1,0,1,<strong><u>0</u></strong>,1] -> [1,0,<strong><u>1</u></strong>,0,1] -> [1,0,0,<strong><u>0</u></strong>,1] -> [1,0,0,0,<strong><u>1</u></strong>] -> [1,0,0,<strong><u>0</u></strong>,0] -> [1,0,<strong><u>0</u></strong>,0,0] -> [1,<strong><u>0</u></strong>,0,0,0] -> [<strong><u>1</u></strong>,0,0,0,0] -> [0,0,0,0,0].</code></li>
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</ul>
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</li>
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</ul>
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</div>
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<p><strong class="example">Example 2:</strong></p>
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<div class="example-block">
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<p><strong>Input:</strong> <span class="example-io">nums = [2,3,4,0,4,1,0]</span></p>
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<p><strong>Output:</strong> <span class="example-io">0</span></p>
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<p><strong>Explanation:</strong></p>
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<p>There are no possible valid selections.</p>
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</div>
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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>1 <= nums.length <= 100</code></li>
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<li><code>0 <= nums[i] <= 100</code></li>
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<li>There is at least one element <code>i</code> where <code>nums[i] == 0</code>.</li>
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</ul>
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