simple python solution to puddle problem found here: http://qandwhat.apps.runkite.com/i-failed-a-twitter-interview/

gistfile1.py

# Python solution to the puddle problem
# from: http://qandwhat.apps.runkite.com/i-failed-a-twitter-interview/
#
# single pass, streaming capable. O(n), memory as much as wall size.
# 
def calc_vol(a):
    vol = 0
    count = [0]
    maxi = 0
    last = 0
    for w in a:
        if w >= maxi:
            print "new max!"
            for i in range(maxi,w):
                count.append(0)
            maxi = w
        else:
            print "smaller than current max!"
            for i in range(w,maxi):
                count[i] += 1
            print count
        if w > last:
            for i in range(0,w):
                vol += count[i]
                count[i] = 0
            print "adding to vol = %d" % vol
        last = w
    print "volume is: %d" % vol
    return vol