Ambiguous Coordinates — LeetCode 816 Python Solution

The problem

We had some 2-dimensional coordinates, like "(1, 3)" or "(2, 0.5)". Then, we removed all commas, decimal points, and spaces and ended up with the string s.

Example

Input

s = "(123)"

Output

["(1, 2.3)","(1, 23)","(1.2, 3)","(12, 3)"]

Python solution

class Solution:
    def ambiguousCoordinates(self, s: str) -> List[str]:
        def f(i, j):
            res = []
            for k in range(1, j - i + 1):
                l, r = s[i : i + k], s[i + k : j]
                ok = (l == '0' or not l.startswith('0')) and not r.endswith('0')
                if ok:
                    res.append(l + ('.' if k < j - i else '') + r)
            return res

        n = len(s)
        return [
            f'({x}, {y})' for i in range(2, n - 1) for x in f(1, i) for y in f(i, n - 1)
        ]

Complexity

Pattern: Backtracking

Build candidates one choice at a time and abandon a branch the moment it cannot work. LeetCode 816. Ambiguous Coordinates is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Backtracking.

The backtracking guide has the Python template for the pattern and the 105 LeetCode problems that use it.

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