Leetcode #68: Text Justification
In this guide, we solve Leetcode #68 Text Justification 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 an array of strings words and a width maxWidth, format the text such that each line has exactly maxWidth characters and is fully (left and right) justified. You should pack your words in a greedy approach; that is, pack as many words as you can in each line.
Quick Facts
- Difficulty: Hard
- Premium: No
- Tags: Array, String, Simulation
Intuition
We need to scan characters while tracking positions or counts.
A simple state machine keeps the logic precise.
Approach
Iterate through the string once and update the state for each character.
Use a map or array if you need fast lookups.
Steps:
- Iterate through characters.
- Maintain necessary state.
- Build or validate the output.
Example
Input: words = ["This", "is", "an", "example", "of", "text", "justification."], maxWidth = 16
Output:
[
"This is an",
"example of text",
"justification. "
]
Python Solution
class Solution:
def fullJustify(self, words: List[str], maxWidth: int) -> List[str]:
ans = []
i, n = 0, len(words)
while i < n:
t = []
cnt = len(words[i])
t.append(words[i])
i += 1
while i < n and cnt + 1 + len(words[i]) <= maxWidth:
cnt += 1 + len(words[i])
t.append(words[i])
i += 1
if i == n or len(t) == 1:
left = ' '.join(t)
right = ' ' * (maxWidth - len(left))
ans.append(left + right)
continue
space_width = maxWidth - (cnt - len(t) + 1)
w, m = divmod(space_width, len(t) - 1)
row = []
for j, s in enumerate(t[:-1]):
row.append(s)
row.append(' ' * (w + (1 if j < m else 0)))
row.append(t[-1])
ans.append(''.join(row))
return ans
Complexity
The time complexity is , and the space complexity is . The space complexity is .
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.