largestAltitude

#prefix sum exercise.
# 1. create a new array 2. first element needs to be copied
# 3. do the cumulative sum
# made some comments

class Solution:
    def longestAltitude(self, gain):
        
        n = len(gain)
       
        
        # [0] is an array with a zero element
        # need to create a new array for prefix sum
        # but in order to get a zero need to do (n+1) below
        prefix_sum = [0] * (n+1)
        prefix_sum[0] = gain[0]
        print(prefix_sum)
        
        #trick: if zero is not in the input arr
        #then how do you take into acct?????
        #-4,-3,-2,-1,4,3,2
        for i in range(1, n):
            prefix_sum[i] = prefix_sum[i-1] + gain[i]
            print(prefix_sum[i])
            print(prefix_sum[i-n])
            print(gain[i])
        return max(prefix_sum)
            
        
      
myVar = Solution()     
myVar.longestAltitude([-4,-3,-2,-1,4,3,2])