Merge pull request neetcode-gh#1096 from ritesh-dt/main

Add solution for 73 - Set Matrix Zeroes in C

Author: Ahmad-A0

c/73-Set-Matrix-Zeroes.c

@@ -0,0 +1,61 @@
+/*
+    Given a 2d matrix if an element is 0, set it's entire row and column to 0 as
+    well.
+    Ex. matrix = [[ 1,  1,  1],         [[ 1,  0,  1],
+                  [ 1,  0,  1],    ->    [ 0,  0,  0],
+                  [ 1,  1,  1]]          [ 1,  0,  1]]
+
+    An identical result matrix can be initialised and then updated according to 
+    the zeros values in the original matrix. However, this would take O(m*n) 
+    space, which can be improved.
+    
+    By doing the updations in the same matrix, space complexity becomes O(1). We
+    reserve the top most row as marker, they will signify whether the 
+    corresponding column has a zero or not. Similarly the first column, will do
+    the same for the rows. 
+    
+    An additional variable is needed as the m[0][0] is common in both the first
+    row and first column.
+
+    Time: O(m*n) where m, n are the matrix dimensions
+    Space: O(1)
+*/
+
+void setZeroes(int** matrix, int matrixSize, int* matrixColSize){
+    int ROW = matrixSize;
+    int COL = *matrixColSize;
+    bool rowZero = false;
+    
+    for (int r = 0; r < ROW; ++r) {
+        for (int c = 0; c < COL; ++c) {
+            if (matrix[r][c] == 0) {
+                matrix[0][c] = 0;
+                if (r > 0) 
+                    matrix[r][0] = 0;
+                else
+                    rowZero = true;
+            }
+        }
+    }
+
+    for (int r = 1; r < ROW; ++r) {
+        for (int c = 1; c < COL; ++c) {
+            if (matrix[0][c] == 0 || matrix[r][0] == 0)
+                matrix[r][c] = 0;
+        }
+    }
+
+    // Set first column as zeros if matrix[0][0] is set
+    if (matrix[0][0] == 0) {
+        for (int r = 0; r < ROW; ++r) {
+            matrix[r][0] = 0;
+        }
+    }
+
+    // Set first row as zeros if rowZero is true
+    if (rowZero) {
+        for (int c = 0; c < COL; ++c) {
+            matrix[0][c] = 0;
+        }
+    }
+}