Leetcode: Daily Temperatures

Daily Temperatures

Similar Problems:

Given a list of daily temperatures, produce a list that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.

For example, given the list temperatures = [73, 74, 75, 71, 69, 72, 76, 73], your output should be [1, 1, 4, 2, 1, 1, 0, 0].

Note: The length of temperatures will be in the range [1, 30000]. Each temperature will be an integer in the range [30, 100].

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## Blog link: https://code.dennyzhang.com/daily-temperatures
## Basic Ideas: Monotonous stack can help us find first largest element in O(n) time complexity.
##              Descending stack: find the next bigger nubmer for each element
##              For any given number, if we haven't met the bigger number. We push it to the stack
##              If we pop out one element, we do find a bigger number than this element.
## Complexity: Time O(n), Space O(n)
class Solution(object):
    def dailyTemperatures(self, temperatures):
        :type temperatures: List[int]
        :rtype: List[int]
        length = len(temperatures)
        res = [0]*length
        stack = []
        for i in xrange(length):
            # If current number is bigger, we solved the previous puzzles
            while len(stack) != 0 and temperatures[i] > temperatures[stack[-1]]:
                k = stack.pop()
                # t[i] is the next bigger number than t[k]
                res[k] = i-k
        return res

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