/*
white = 0, red = 1, blue = 2,
red or blue just moved in = 3 and
red or blue (in the first row or column) just moved out = 4
*/
int grid[n][n]; /* grid[row][col] */
bool finished = false;
int n_itrs = 0;
int redcount, bluecount;
int i, j;
…
while (!finished && n_itrs < MAX_ITRS){ /* count the number of red and blue in each tile and check if the computation can be terminated*/ ... n_itrs++; /* red color movement */ for (i = 0; i < n; i++){ if (grid[i][0] == 1 && grid[i][1] == 0){ grid[i][0] = 4; grid[i][1] = 3; } for (j = 1; j < n; j++){ if (grid[i][j] == 1 && (grid[i][(j+1)%n] == 0){ grid[i][j] = 0; grid[i][(j+1)%n] = 3; } else if (grid[i][j] == 3) grid[i][j] = 1; } if (grid[i][0] == 3) grid[i][0] = 1; else if (grid[i][0] == 4) grid[i][0] = 0; } /* blue color movement */ for (j = 0; j < n; j++){ ... } }