第一个题目为括号匹配比较简单，省略
力扣题目连接：最小栈
需要用一个辅助栈，每次入栈和出栈时辅助栈同步入栈出栈，这个辅助栈的入栈值为当前栈的最小元素
class MinStack {
Deque<Integer> xStack;
Deque<Integer> minStack;
public MinStack() {
xStack = new LinkedList<Integer>();
minStack = new LinkedList<Integer>();
minStack.push(Integer.MAX_VALUE);
}
public void push(int val) {
xStack.push(val);
minStack.push(Math.min(minStack.peek(), val));
}
public void pop() {
xStack.pop();
minStack.pop();
}
public int top() {
return xStack.peek();
}
public int getMin() {
return minStack.peek();
}
}
/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.push(val);
* obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.getMin();
*/2026/3/24小于 1 分钟