384. 打乱数组

打乱一个没有重复元素的数组。

示例:

1. // 以数字集合 1, 2 和 3 初始化数组。
   int[] nums = {1,2,3};
   Solution solution = new Solution(nums);
2. // 打乱数组 [1,2,3] 并返回结果。任何 [1,2,3]的排列返回的概率应该相同。
   solution.shuffle();
3. // 重设数组到它的初始状态[1,2,3]。
   solution.reset();
4. // 随机返回数组[1,2,3]打乱后的结果。
   solution.shuffle();
   代码如下：

class Solution:

    def __init__(self, nums):
        """
        :type nums: List[int]
        """
        self.origin = nums

    def reset(self):
        """
        Resets the array to its original configuration and return it.
        :rtype: List[int]
        """
        return self.origin

    def shuffle(self):
        """
        Returns a random shuffling of the array.
        :rtype: List[int]
        """
        import random
        random_Nums = self.origin[:]
        random.shuffle(random_Nums)
        return random_Nums


# Your Solution object will be instantiated and called as such:
# obj = Solution(nums)
# param_1 = obj.reset()
# param_2 = obj.shuffle()

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。

示例:

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.

代码如下

class MinStack:

    def __init__(self):
        """
        initialize your data structure here.
        """
        self.stack = []
        self.min_stack = []

    def push(self, x):
        """
        :type x: int
        :rtype: void
        """
        self.stack.append(x)
        if len(self.min_stack) == 0 or self.min_stack[-1] >= x:
            self.min_stack.append(x)

    def pop(self):
        """
        :rtype: void
        """
        p = self.stack.pop()
        if p == self.min_stack[-1]:
            self.min_stack.pop()

    def top(self):
        """
        :rtype: int
        """
        return self.stack[-1]

    def getMin(self):
        """
        :rtype: int
        """
        return self.min_stack[-1]


# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(x)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()

互相学习，互相指教。