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45 lines
1.6 KiB
HTML
45 lines
1.6 KiB
HTML
<p>Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.</p>
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<p>Implement the <code>MinStack</code> class:</p>
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<ul>
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<li><code>MinStack()</code> initializes the stack object.</li>
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<li><code>void push(int val)</code> pushes the element <code>val</code> onto the stack.</li>
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<li><code>void pop()</code> removes the element on the top of the stack.</li>
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<li><code>int top()</code> gets the top element of the stack.</li>
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<li><code>int getMin()</code> retrieves the minimum element in the stack.</li>
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</ul>
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<p>You must implement a solution with <code>O(1)</code> time complexity for each function.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["MinStack","push","push","push","getMin","pop","top","getMin"]
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[[],[-2],[0],[-3],[],[],[],[]]
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<strong>Output</strong>
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[null,null,null,null,-3,null,0,-2]
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<strong>Explanation</strong>
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MinStack minStack = new MinStack();
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minStack.push(-2);
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minStack.push(0);
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minStack.push(-3);
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minStack.getMin(); // return -3
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minStack.pop();
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minStack.top(); // return 0
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minStack.getMin(); // return -2
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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>-2<sup>31</sup> <= val <= 2<sup>31</sup> - 1</code></li>
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<li>Methods <code>pop</code>, <code>top</code> and <code>getMin</code> operations will always be called on <strong>non-empty</strong> stacks.</li>
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<li>At most <code>3 * 10<sup>4</sup></code> calls will be made to <code>push</code>, <code>pop</code>, <code>top</code>, and <code>getMin</code>.</li>
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</ul>
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