You are doing a mistake here , you are not taking input completely. You are comparing arr[i+1][j] etc. directly but you have not taken input for that . In your IDE , you may be using new compiler which sets default value zero or something else , which is not causing trouble . But CF judges are initialsing array with values which are causing trouble .Either use 2D vector , which default initialises to zero (As here zero will not cause trouble because no color is zero here ) or take input first . Issue is of default initialisation .