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Author: 10coder

SetMatrixZeroes.java

@@ -0,0 +1,84 @@
+// https://leetcode.com/problems/set-matrix-zeroes/
+public class SetMatrixZeroes {
+
+    //Approach: traverse through the matrix and mark those rows and cols which needs to be turned zero at 0th row and 0th col.
+    //Also have 2 variable flags to determine if 0th row and 0th col needs to be zeored
+    //Time: O(mn)
+    //Space: O(1)
+    public void setZeroes(int[][] matrix) {
+        boolean isr=false,isc=false;
+        for(int i=0;i<matrix.length;i++) {
+            for(int j=0;j<matrix[0].length;j++) {
+                if(i==0 && matrix[i][j]==0) {
+                    isr=true;
+                }
+                if(j==0 && matrix[i][j]==0) {
+                    isc=true;
+                }
+                if(i!=0 && j!=0 && (matrix[i][j]==0)) {
+                    //if {
+                    matrix[i][0]=0;
+                    matrix[0][j]=0;
+                    //}
+                }
+            }
+
+        }
+
+        for(int i=1;i<matrix.length;i++) {
+            for(int j=1;j<matrix[0].length;j++) {
+                if(matrix[i][0]==0 || matrix[0][j]==0) {
+                    matrix[i][j]=0;
+                }
+            }
+        }
+
+        // System.out.println(isr +"--- "+isc);
+
+        if(isc) {
+            int i=0;
+            while(i<matrix.length) {
+                matrix[i++][0]=0;
+            }
+        }
+
+        if(isr) {
+            int j=0;
+            while(j<matrix[0].length) {
+                matrix[0][j]=0;
+                j++;
+            }
+        }
+    }
+}
+
+//      Apporach: we keep track of all rows and cols to be updated to zeroes
+//Space: O(m+n)
+//Time: O(mn)
+//         public void setZeroes(int[][] matrix) {
+//         List<Integer> rows= new ArrayList<>();
+//         List<Integer> cols = new ArrayList<>();
+//         for(int i=0;i<matrix.length;i++) {
+//             for(int j=0;j<matrix[0].length;j++) {
+//                 if(matrix[i][j]==0) {
+//                     rows.add(i);
+//                     cols.add(j);
+//                 }
+//             }
+//         }
+
+//         for(int r: rows) {
+//             for(int i=0;i<matrix[0].length;i++) {
+//                 matrix[r][i]=0;
+//             }
+//         }
+
+//         for(int c:cols) {
+//             for(int i=0;i<matrix.length;i++) {
+//                 matrix[i][c]=0;
+//             }
+//         }
+
+//     }
+// }
+