πΉ Problem: 3195. Find the Minimum Area to Cover All Ones I
Difficulty: #Medium
Tags: #Array, #Matrix
π Problem Summary
Finding the smallest area rectangle that can cover all
1s in a binary matrix. The rectangle must be axis-aligned and can only contain1s.
π§ My Thought Process
Brute Force Idea:
My solution is kinda brute force, because I will iterate through the entire matrix to find the minimum and maximum row and column indices that contain1s. This gives us the bounds of the rectangle that covers all1s.Optimized Strategy:
Instead of checking every possible rectangle, I directly find the minimum and maximum indices of rows and columns that contain1s. This reduces the problem to a simple calculation of area based on these indices. It's pretty efficient since we only traverse the matrix once.
βοΈ Code Implementation (Python)
# Brief comment about the approach
from typing import List
class Solution:
def minimumArea(self, grid: List[List[int]]) -> int:
rows, cols = len(grid), len(grid[0]) if grid else 0
min_row, max_row = rows, -1
min_col, max_col = cols, -1
for i in range(rows):
for j in range(cols):
if grid[i][j] == 1:
min_row = min(min_row, i)
max_row = max(max_row, i)
min_col = min(min_col, j)
max_col = max(max_col, j)
if max_row == -1:
return 0
return (max_row - min_row + 1) * (max_col - min_col + 1)
β±οΈ Time & Space Complexity
- Time: O(rows * cols) - We traverse the entire matrix once.
- Space: O(1) - We use a constant amount of space for variables.
π§© Key Takeaways
- β What concept or trick did I learn? Nothing new, just a straightforward application of finding bounds in a matrix.
- π‘ What made this problem tricky?
The tricky part was ensuring that I correctly identified the bounds of the rectangle and handled edge cases where there are no
1s. - π How will I recognize a similar problem in the future? Look for problems that require finding bounds or areas in a grid or matrix, especially when dealing with binary values.
π Reflection (Self-Check)
- [x] Could I solve this without help?
- [x] Did I write code from scratch?
- [x] Did I understand why it works?
- [x] Will I be able to recall this in a week?
π Progress Tracker
| Metric | Value |
|---|---|
| Day | 64 |
| Total Problems Solved | 425 |
| Confidence Today | π |
| Leetcode Rating |
1530 π |
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