2022-2-24
剑指 Offer 30. 包含min函数的栈
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.
class MinStack {
Stack<Integer> A, B;
public MinStack() {
A = new Stack<>();
B = new Stack<>();
}
public void push(int x) {
A.push(x);
if(B.empty() || B.peek() >= x)
B.push(x);
}
public void pop() {
if(A.pop().equals(B.peek()))
B.pop();
}
public int top() {
return A.peek();
}
public int min() {
return B.peek();
}
}
/**
* 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();
*/
