Create 0073-set-matrix-zeroes.java

Author: sanajitjana

Medium/0073-set-matrix-zeroes.java

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+/**
+ * Problem: 73. Set Matrix Zeroes
+ * Difficulty: Medium
+ * URL: https://leetcode.com/problems/set-matrix-zeroes/
+ * 
+ * Approach:
+ * - Use the first row and first column as markers to record which rows/columns should be zeroed.
+ * - Track separately if the first row or first column need to be zeroed to avoid losing marker info.
+ * - In the second pass, set entire rows/columns to zero based on these markers.
+ * 
+ * Time Complexity: O(m * n)  // each cell is visited a constant number of times
+ * Space Complexity: O(1)    // in-place, only a few extra variables
+ */
+
+class Solution {
+    public void setZeroes(int[][] matrix) {
+        int m = matrix.length;
+        int n = matrix[0].length;
+
+        boolean r0F = false;
+        boolean c0F = false;
+
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (i == 0 && matrix[i][j] == 0) r0F = true;
+                if (j == 0 && matrix[i][j] == 0) c0F = true;
+                if (matrix[i][j] == 0) {
+                    matrix[0][j] = 0;
+                    matrix[i][0] = 0;
+                }
+            }
+        }
+
+        for (int i = 1; i < n; i++) {
+            if (matrix[0][i] == 0) {
+                for (int j = 0; j < m; j++) {
+                    matrix[j][i] = 0;
+                }
+            }
+        }
+
+        for (int i = 1; i < m; i++) {
+            if (matrix[i][0] == 0) {
+                for (int j = 0; j < n; j++) {
+                    matrix[i][j] = 0;
+                }
+            }
+        }
+
+        if (r0F) {
+            for (int i = 0; i < n; i++) {
+                matrix[0][i] = 0;
+            }
+        }
+
+        if (c0F) {
+            for (int i = 0; i < m; i++) {
+                matrix[i][0] = 0;
+            }
+        }
+    }
+}