Suppose we have a list of stacks, we can take any stack or stacks and pop any number of elements from it. We have to find the maximum sum that can be achieved such that all stacks have the same sum value.
So, if the input is like stacks = [[3, 4, 5, 6], [5, 6, 1, 4, 4], [10, 2, 2, 2] ], then the output will be 12, as we can take operations like −
Pop [6] from the first stack we get [3, 4, 5] the sum is 12.
Pop [4,4] from the second stack we get [5, 6, 1] the sum is 12.
Pop [2,2] from the third stack we get [10, 2] the sum is 12.
To solve this, we will follow these steps −
sums := an empty map
for each stk in stacks, do
s := 0
for each n in stk, do
s := s + n
sums[s] := sums[s] + 1
ans := 0
for each key value pairs (s, f) of sums, do
if f >= stack count and s > ans, then
ans := s
return ans
Let us see the following implementation to get better understanding −
Example
from collections import defaultdict class Solution: def solve(self, stacks): sums = defaultdict(int) for stk in stacks: s = 0 for n in stk: s += n sums[s] += 1 ans = 0 for s, f in sums.items(): if f >= len(stacks) and s > ans: ans = s return ans ob1 = Solution() stacks = [ [3, 4, 5, 6], [5, 6, 1, 4, 4], [10, 2, 2, 2] ] print(ob1.solve(stacks))
Input
stacks = [ [3, 4, 5, 6], [5, 6, 1, 4, 4], [10, 2, 2, 2] ]
Output
12