自己写的，还没有看答案
class Solution {
public void setZeroes(int[][] matrix) {
if (matrix.length == 0) return;
int m = matrix.length, n = matrix[0].length;
HashSet<Integer> setA = new HashSet<>();
HashSet<Integer> setB = new HashSet<>();
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (matrix[i][j] == 0){
setA.add(i);
setB.add(j);
}
}
}
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (setA.contains(i) || setB.contains(j)) {
matrix[i][j] = 0;
}
}
}
}
}