Leetcode #1016: Binary String With Substrings Representing 1 To N
In this guide, we solve Leetcode #1016 Binary String With Substrings Representing 1 To N in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Given a binary string s and a positive integer n, return true if the binary representation of all the integers in the range [1, n] are substrings of s, or false otherwise. A substring is a contiguous sequence of characters within a string.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Bit Manipulation, Hash Table, String, Sliding Window
Intuition
Fast membership checks and value lookups are the heart of this problem, which makes a hash map the natural choice.
By storing what we have already seen (or counts/indexes), we can answer the question in one pass without backtracking.
Approach
Scan the input once, using the map to detect when the condition is satisfied and to update state as you go.
This keeps the solution linear while remaining easy to explain in an interview setting.
Steps:
- Initialize a hash map for seen items or counts.
- Iterate through the input, querying/updating the map.
- Return the first valid result or the final computed value.
Example
Input: s = "0110", n = 3
Output: true
Python Solution
class Solution:
def queryString(self, s: str, n: int) -> bool:
if n > 1000:
return False
return all(bin(i)[2:] in s for i in range(n, n // 2, -1))
Complexity
The time complexity is and the space complexity is , where is the length of string and is the positive integer given in the problem. The space complexity is , where is the length of string and is the positive integer given in the problem.
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.