Daily Temperatures.py

'''
 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]. 
'''

class Solution(object):
    def dailyTemperatures(self, temperatures):
        """
        :type temperatures: List[int]
        :rtype: List[int]
        """
        
        res = [0 for i in xrange(len(temperatures))]
        stack = []
        for i in xrange(len(temperatures)):
            if not stack:
                stack.append(i)
            else:
                while stack and temperatures[stack[-1]] < temperatures[i]:
                    res[stack[-1]] = i - stack[-1]
                    stack.pop()
                stack.append(i)
                
        return res