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Find pairs with given sum such that pair elements lie in different BSTs in Python
Suppose we have two given Binary Search Trees and another sum is given; we have to find pairs with respect of given sum so that each pair elements must be in different BSTs.
So, if the input is like sum = 12
then the output will be [(6, 6), (7, 5), (9, 3)]
To solve this, we will follow these steps −
Define a function solve() . This will take trav1, trav2, Sum
left := 0
right := size of trav2 - 1
res := a new list
while left < size of trav1 and right >= 0, do
if trav1[left] + trav2[right] is same as Sum, then
insert (trav1[left],trav2[right]) at the end of res
left := left + 1
right := right - 1
otherwise when (trav1[left] + trav2[right]) < Sum, then
left := left + 1
otherwise,
right := right - 1
return res
From the main method do the following −
trav1 := a new list, trav2 := a new list
trav1 := in order traversal of tree1
trav2 := in order traversal of tree2
return solve(trav1, trav2, Sum)
Example (Python)
Let us see the following implementation to get better understanding −
class ListNode: def __init__(self, data): self.data = data self.left = None self.right = None def insert(root, key): if root == None: return ListNode(key) if root.data > key: root.left = insert(root.left, key) else: root.right = insert(root.right, key) return root def storeInorder(ptr, traversal): if ptr == None: return storeInorder(ptr.left, traversal) traversal.append(ptr.data) storeInorder(ptr.right, traversal) def solve(trav1, trav2, Sum): left = 0 right = len(trav2) - 1 res = [] while left < len(trav1) and right >= 0: if trav1[left] + trav2[right] == Sum: res.append((trav1[left],trav2[right])) left += 1 right -= 1 elif trav1[left] + trav2[right] < Sum: left += 1 else: right -= 1 return res def get_pair_sum(root1, root2, Sum): trav1 = [] trav2 = [] storeInorder(root1, trav1) storeInorder(root2, trav2) return solve(trav1, trav2, Sum) root1 = None for element in [9,11,4,7,2,6,15,14]: root1 = insert(root1, element) root2 = None for element in [6,19,3,2,4,5]: root2 = insert(root2, element) Sum = 12 print(get_pair_sum(root1, root2, Sum))
Input
[9,11,4,7,2,6,15,14], [6,19,3,2,4,5], 12
Output
[(6, 6), (7, 5), (9, 3)]
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