3905. Multi Source Flood Fill

You are given two integers n and m representing the number of rows and columns of a grid, respectively. You are also given a 2D integer array sources, where sources[i] = [ri, ci, color​​​​​​​i] indicates that the cell (ri, ci) is initially colored with colori. All other cells are initially uncolored and represented as 0. At each time step, every currently colored cell spreads its color to all ad