How hard is LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?

LeetCode 1536. Minimum Swaps to Arrange a Binary Grid is rated Medium on LeetCode.

What is the time complexity of LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?

The Python solution on this page runs in O(n^2).

What is the space complexity of LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?

The Python solution on this page uses O(n) auxiliary space.

What topics does LeetCode 1536. Minimum Swaps to Arrange a Binary Grid cover?

LeetCode 1536. Minimum Swaps to Arrange a Binary Grid is tagged Greedy, Array and Matrix on LeetCode.

Minimum Swaps to Arrange a Binary Grid — LeetCode 1536 Python Solution

MediumGreedyArrayMatrix

Problem: #1536
Pattern: Matrix and Grid
Reading time: 4 min
Source: leetcode.com

The problem

Given an n x n binary grid, in one step you can choose two adjacent rows of the grid and swap them. A grid is said to be valid if all the cells above the main diagonal are zeros.

Example

Input: grid = [[0,0,1],[1,1,0],[1,0,0]]
Output: 3

Python solution

Python

class Solution:
    def minSwaps(self, grid: List[List[int]]) -> int:
        n = len(grid)
        pos = [-1] * n
        for i in range(n):
            for j in range(n - 1, -1, -1):
                if grid[i][j] == 1:
                    pos[i] = j
                    break
        ans = 0
        for i in range(n):
            k = -1
            for j in range(i, n):
                if pos[j] <= i:
                    ans += j - i
                    k = j
                    break
            if k == -1:
                return -1
            while k > i:
                pos[k], pos[k - 1] = pos[k - 1], pos[k]
                k -= 1
        return ans

Complexity

Measure	Complexity
Time	O(n^2)
Space	O(n) auxiliary

Pattern: Matrix and Grid

Treat a 2-D grid as a graph whose neighbours are the four adjacent cells. LeetCode 1536. Minimum Swaps to Arrange a Binary Grid is filed here because LeetCode tags it Matrix, which is the vocabulary this hub collects.

The matrix and grid guide has the Python template for the pattern and the 216 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?: LeetCode 1536. Minimum Swaps to Arrange a Binary Grid is rated Medium on LeetCode.
What is the time complexity of LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?: The Python solution on this page runs in O(n^2).
What is the space complexity of LeetCode 1536. Minimum Swaps to Arrange a Binary Grid?: The Python solution on this page uses O(n) auxiliary space.
What topics does LeetCode 1536. Minimum Swaps to Arrange a Binary Grid cover?: LeetCode 1536. Minimum Swaps to Arrange a Binary Grid is tagged Greedy, Array and Matrix on LeetCode.