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30-包含min函数的栈
题目描述
https://leetcode.cn/problems/bao-han-minhan-shu-de-zhan-lcof
定义栈的数据结构，请在该类型中实现一个能够得到栈的最小元素的 min 函数在该栈中，调用 min、push 及 pop 的时间复杂度都是 O(1)。
示例:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.min(); --> 返回 -3.
minStack.pop();
minStack.top(); --> 返回 0.
minStack.min(); --> 返回 -2.
提示：
各函数的调用总次数不超过 20000 次
注意：本题与主站 155 题相同：https://leetcode.cn/problems/min-stack/
思路分析
实现代码
csharp
public class MinStack {
private Stack<int> stack = new Stack<int>();
private Stack<int> minStack = new Stack<int>();
private int minValue = Int32.MaxValue;
/** initialize your data structure here. */
public MinStack() {
}
public void Push(int x) {
stack.Push(x);
minValue = minValue > x ? x : minValue;
minStack.Push(minValue);
}
public int Pop() {
minStack.Pop();
minValue = minStack.Count == 0 ? Int32.MaxValue : minStack.Peek();
return stack.Pop();
}
public int Top() {
return stack.Peek();
}
public int Min() {
return minValue;
}
}
/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.Push(x);
* obj.Pop();
* int param_3 = obj.Top();
* int param_4 = obj.Min();
*/