dsa · easy

Shared Tail of Two Lists

Two singly linked lists are given by their node-value arrays head_a and head_b. They may share a tail: a non-empty suffix of equal values that both chains keep to the end. Return the first value of that shared suffix. If the two arrays share no suffix, return 0.

Arguments

• head_a — node values of the first list, front to back; [] if empty
• head_b — node values of the second list, front to back; [] if empty

Values are positive, so 0 cannot be a real node value.

Example

head_a = [4,1,8,4,5], head_b = [5,0,8,4,5]

Reading from the back, both end …, 8, 4, 5. The first shared tail value is 8.

[2,3] and [7,9] share no suffix → 0.

Constraints

0 <= head_a.length, head_b.length <= 4*10^4 1 <= node value <= 10^5 Hidden tests include near-max size for this bound; a slower-than-intended solution TLEs.

Examples

Example 1

Input:
[4,1,8,4,5]
[5,0,8,4,5]

Expected:
8

Example 2

Input:
[2,3]
[7,9]

Expected:
0

Example 3

Input:
[1,2,3]
[1,2,3]

Expected:
1

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