Lazy Snakes and Ladders P37743


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Snakes and Ladders has amused children for generations. So, after the failure of his fifth start-up on a row, Edgar Hausdorff decides to go with that theme for the first app of his newly founded Hausdorff Space mobile game development company. The rules are simple:

  • Players red and blue start with their counters on cell number 1, and take turns in rolling a six-sided die, with red going first.
  • The counter for the current player moves forward the number of cells rolled in the die (e.g., rolling a 5 when on cell 4 takes the counter to 9).
  • The goal is to reach the cell 100. An exact roll is needed: in case of excess, the counter bounces and moves the extra count backwards (e.g., rolling a 5 when on cell 97 takes the counter to 98).
  • If the landing cell (after potential bouncing) is the bottom of a ladder, the counter is moved to its top, which will be a higher-numbered cell (e.g., rolling a 1 when on cell 1 takes the counter to 38). Nothing happens when the counter directly lands on a top.
  • If the landing cell (after potential bouncing) is the head of a snake, the counter is moved to its tail, which will be a lower-numbered one (e.g., rolling a 3 when on cell 98 takes the counter to 80). Nothing happens when the counter directly lands on a tail.
  • If the rolled number was six, the player keeps the turn; otherwise, it passes to the other player (irrespective of whether bouncing, snakes, or ladders were involved).

However, Hausdorff’s lack of coding skills and moral decency makes him cut corners when implementing the code for die rolling. He grabs a real die, rolls it n times writing down each outcome ri, and implements the rolls in the game by returning those values in cyclic sequence. Using the board depicted in the image, can you tell the winner given the numbers that Hausdorff rolled? Every given case is guaranteed to eventually finish.


Input consists of several cases, each with n followed by the ri’s, with 1 ≤ ri ≤ 6.


For each case, print “RED” or “BLUE” depending on the winner.

Public test cases
  • Input

    1  3
    2  3 1
    5  3 6 4 5 3
    7  3 6 4 5 3 2 3


  • Information
    Edgar Gonzàlez
    Official solutions
    User solutions
    Quinzè Concurs de Programació de la UPC - Final