Leetcode #1347: Minimum Number of Steps to Make Two Strings Anagram

In this guide, we solve Leetcode #1347 Minimum Number of Steps to Make Two Strings Anagram 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

You are given two strings of the same length s and t. In one step you can choose any character of t and replace it with another character.

Quick Facts

• Difficulty: Medium
• Premium: No
• Tags: Hash Table, String, Counting

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

Python Solution

Complexity

The time complexity is $O(m + n)$, and the space complexity is $O(|\Sigma|)$, where $m$ and $n$ are the lengths of the strings $\textit{s}$ and $\textit{t}$, respectively, and $|\Sigma|$ is the size of the character set. The space complexity is $O(|\Sigma|)$, where $m$ and $n$ are the lengths of the strings $\textit{s}$ and $\textit{t}$, respectively, and $|\Sigma|$ is the size of the character set.

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.