 ### Flood Fill Algorithm

Problem-Given a 2D matrix,location of a point and a variable k.Our task is to change the value of given location and its adjacent position(except diagonals) having same values as that of given location with the variable k.
Approach-problem can easily be solved by using DFS in Graph.Make a function which takes input of location.Change the color of it and then recursively call the function for its adjascent sides.

//Code starts here
#include <iostream> using namespace std; const int M = 100, N = 100; int a[M][N]; int m, n; void floodfill(int x, int y, int old, int newc) { if (x >= m || y >= n || x < 0 || y < 0) { return; } if (a[x][y] == old) { a[x][y] = newc; floodfill(x + 1, y, old, newc); floodfill(x, y + 1, old, newc); floodfill(x - 1, y, old, newc); floodfill(x, y - 1, old, newc); } } int main() { int t; cin >> t; while (t--) { cin >> m >> n; for (int i = 0; i < m; i++) { for (int j = 0; j < n; j++) { cin >> a[i][j]; } } int x, y, k, old; cin >> x >> y >> k; old = a[x][y]; floodfill(x, y, old, k); for (int i = 0; i < m; i++) { for (int j = 0; j < n; j++) { cout << a[i][j] << " "; } //cout<<endl; } cout << endl; } return 0; }
//code ends here

Input:
3
3 4
0 1 1 0 1 1 1 1 0 1 2 3
0 1 5
2 2
1 1 1 1
0 1 8
4 4
1 2 3 4 1 2 3 4 1 2 3 4 1 3 2 4
0 2 9

Output:
0 5 5 0 5 5 5 5 0 5 2 3
8 8 8 8
1 2 9 4 1 2 9 4 1 2 9 4 1 3 2 4 