feat: solve set matrix zeroes

Author: GangBean

set-matrix-zeroes/GangBean.java

@@ -0,0 +1,40 @@
+class Solution {
+    /**
+    1. understanding
+    - iterate over all cells, if value is 0, then add row and col to sweep target set.
+    - for each row target set, and col target set, sweep all it's value to 0
+    2. complexity
+    - time: O(m * n)
+    - space: O(m + n)
+     */
+    public void setZeroes(int[][] matrix) {
+        Set<Integer> rows = new HashSet<>(); // O(m)
+        Set<Integer> cols = new HashSet<>(); // O(n)
+
+        for (int row = 0; row < matrix.length; row++) { // O(m)
+            for (int col = 0; col < matrix[row].length; col++) { // O(n)
+                if (matrix[row][col] == 0) { // O(m * n)
+                    rows.add(row);
+                    cols.add(col);
+                }
+            }
+        }
+
+        for (int row: rows) { // O(m)
+            int col = 0;
+            while (col < matrix[row].length) { // O(n)
+                matrix[row][col] = 0;
+                col++;
+            }
+        }
+
+        for (int col: cols) { // O(n)
+            int row = 0;
+            while (row < matrix.length) { // O(m)
+                matrix[row][col] = 0;
+                row++;
+            }
+        }
+    }
+}
+