####################
Question 1a
####################
>>> largest_34([1000, 1, 100, 2, 99, 200, -100])
199
>>> largest_34([1000, 1, 100, 2, 99, 200, 20000])
300
>>> 
runtime analysis:O(n)
####################
Question 1b
####################
>>> largest_third([1000, 1, 100, 2, 99, 200, -100])
1200
>>> largest_third([1000,500,200])
1000
>>> largest_third([3000,500,200])
3000
>>>
runtime analysis:O(n)
####################
Question 1c
####################
>>> third_at_least([1000, 1, 100, 2,100, 100, 100])
100
>>> third_at_least([1000, 1, 100, 2, 99, 100, 100])
100
>>> third_at_least([1000, 1, 100, 2,10, 100, 1])
>>> 
runtime analysis:O(n)
####################
Question 1d
####################
>>> a=[1, 1, 5, 8, 2, 6]
>>> x=1000
>>> sum_tri(a,x)
False
>>> x=7
>>> sum_tri(a,x)
True
>>> 
>>> a=[-1, 1, 5, 8, 2, 6]
>>> x=-3
>>> sum_tri(a, x)
True
>>>
runtime anaysis:O(n^3)