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

Add solution for 73 - Set Matrix Zeroes in C

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;
+ }
+ }
+}