73. 矩阵置零

中等

题目描述

解法思路：首先通过遍历记录哪些行和列需要置 0，再遍历一次将 0 填充

Java

class Solution {
    public void setZeroes(int[][] matrix) {
		HashSet<Integer> rows = new HashSet<>();
		HashSet<Integer> cols = new HashSet<>();
		for (int r = 0; r < matrix.length; r++) {
			for (int c = 0; c < matrix[0].length; c++) {
				if (matrix[r][c] == 0) {
					rows.add(r);
					cols.add(c);
				}
			}
		}
		for (int r = 0; r < matrix.length; r++) {
			for (int c = 0; c < matrix[0].length; c++) {
				if (rows.contains(r)) {
					matrix[r][c] = 0;
				}
				if (cols.contains(c)) {
					matrix[r][c] = 0;
				}
			}
		}

	}
}

Python

class Solution:
    def setZeroes(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        rows = set()
        cols = set()
        
        # 记录需要置零的行和列
        for r in range(len(matrix)):
            for c in range(len(matrix[0])):
                if matrix[r][c] == 0:
                    rows.add(r)
                    cols.add(c)
        
        # 将对应的行和列置零
        for r in range(len(matrix)):
            for c in range(len(matrix[0])):
                if r in rows or c in cols:
                    matrix[r][c] = 0