If you\u2019re preparing for coding interviews, the “Set Matrix Zeroes” problem is a must-know! In this blog, we\u2019ll explain the problem, walk through three solutions (Brute Force, Better, and Optimal), and make everything easy to understand with code comments, dry runs, and clear explanations.<\/p>\n\n\n\n
Here’s the [Problem Link<\/span><\/mark><\/a><\/strong>] to begin with.<\/p>\n\n\n You are given an m x n matrix. If any cell in the matrix is 0, you must set its entire row and column to 0. The operation should be done in-place<\/strong>, meaning you should not use extra space for another matrix.<\/p>\n\n\n\n Input:<\/strong> Output:<\/strong> Explanation:<\/strong><\/p>\n\n\n\n Input:<\/strong> Output:<\/strong> Let\u2019s solve the problem step by step in the simplest way:<\/p>\n\n\n\n This approach is easy to understand but not the most efficient.<\/p>\n\n\n\nWhat Does the Problem Say?<\/h2>\n\n\n\n
Example 1<\/h3>\n\n\n\n
matrix = [[1][1][1],[1][1],[1][1][1]]<\/code><\/p>\n\n\n\n[[1][1],[0,][1]]<\/code><\/p>\n\n\n\n\n
Example 2<\/h3>\n\n\n\n
matrix = [[1],,[1,[1]]<\/code><\/p>\n\n\n\n[[0,1]]<\/code><\/p>\n\n\n\nBrute Force Solution<\/h2>\n\n\n\n
Intuition and Approach<\/h3>\n\n\n\n
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Loop through the matrix. When you find a 0, mark its entire row and column to be set to 0 later. But if you set them to 0 immediately, you might overwrite original values, so we need a way to mark them temporarily.<\/li>\n\n\n\n
We use a special value (like infinity) to mark cells that should become zero, but were not originally zero. This way, we don\u2019t confuse new zeroes with original zeroes.<\/li>\n\n\n\n
After marking, loop again and set all marked cells to 0.<\/li>\n<\/ol>\n\n\n\nCode Implementation<\/h3>\n\n\n\n