[LeetCode] #155 最小栈
设计一个支持 push ,pop ,top 操作,并能在常数时间内检索到最小元素的栈。
push(x) —— 将元素 x 推入栈中。
pop() —— 删除栈顶的元素。
top() —— 获取栈顶元素。
getMin() —— 检索栈中的最小元素。
输入:
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]
输出:
[null,null,null,null,-3,null,0,-2]
解释:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); --> 返回 -3.
minStack.pop();
minStack.top(); --> 返回 0.
minStack.getMin(); --> 返回 -2
双栈法
class MinStack { private Stack<Integer> xStack; private Stack<Integer> minStack; /** initialize your data structure here. */ public MinStack() { xStack = new Stack<Integer>(); minStack = new Stack<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(); } }
单栈法
class MinStack { private Stack<Integer> stack; /** initialize your data structure here. */ public MinStack() { stack = new Stack<>(); } public void push(int val) { if(stack.isEmpty()){ stack.push(val); stack.push(val);
}else{ int tmp = stack.peek(); stack.push(val); if(tmp<val){ stack.push(tmp); }else{ stack.push(val); }
} } public void pop() { stack.pop(); stack.pop(); } public int top() { return stack.get(stack.size()-2); } public int getMin() { return stack.peek(); } }
知识点:无
总结:无