1823. Find the Winner of the Circular Game: AC

src/solution/mod.rs

@@ -1373,3 +1373,4 @@ mod s1817_finding_the_users_active_minutes;
 mod s1818_minimum_absolute_sum_difference;
 mod s1819_number_of_different_subsequences_gcds;
 mod s1822_sign_of_the_product_of_an_array;
+mod s1823_find_the_winner_of_the_circular_game;

src/solution/s1823_find_the_winner_of_the_circular_game.rs

@@ -0,0 +1,83 @@
+/**
+ * [1823] Find the Winner of the Circular Game
+ *
+ * There are n friends that are playing a game. The friends are sitting in a circle and are numbered from 1 to n in clockwise order. More formally, moving clockwise from the i^th friend brings you to the (i+1)^th friend for 1 <= i < n, and moving clockwise from the n^th friend brings you to the 1^st friend.
+ * The rules of the game are as follows:
+ * <ol>
+ * 	Start at the 1^st friend.
+ * 	Count the next k friends in the clockwise direction including the friend you started at. The counting wraps around the circle and may count some friends more than once.
+ * 	The last friend you counted leaves the circle and loses the game.
+ * 	If there is still more than one friend in the circle, go back to step 2 starting from the friend immediately clockwise of the friend who just lost and repeat.
+ * 	Else, the last friend in the circle wins the game.
+ * </ol>
+ * Given the number of friends, n, and an integer k, return the winner of the game.
+ *  
+ * Example 1:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/03/25/ic234-q2-ex11.png" style="width: 500px; height: 345px;" />
+ * Input: n = 5, k = 2
+ * Output: 3
+ * Explanation: Here are the steps of the game:
+ * 1) Start at friend 1.
+ * 2) Count 2 friends clockwise, which are friends 1 and 2.
+ * 3) Friend 2 leaves the circle. Next start is friend 3.
+ * 4) Count 2 friends clockwise, which are friends 3 and 4.
+ * 5) Friend 4 leaves the circle. Next start is friend 5.
+ * 6) Count 2 friends clockwise, which are friends 5 and 1.
+ * 7) Friend 1 leaves the circle. Next start is friend 3.
+ * 8) Count 2 friends clockwise, which are friends 3 and 5.
+ * 9) Friend 5 leaves the circle. Only friend 3 is left, so they are the winner.
+ * Example 2:
+ *
+ * Input: n = 6, k = 5
+ * Output: 1
+ * Explanation: The friends leave in this order: 5, 4, 6, 2, 3. The winner is friend 1.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= k <= n <= 500
+ *
+ *  
+ * Follow up:
+ * Could you solve this problem in linear time with constant space?
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/find-the-winner-of-the-circular-game/
+// discuss: https://leetcode.com/problems/find-the-winner-of-the-circular-game/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn find_the_winner(n: i32, k: i32) -> i32 {
+        (2..=n).fold(0, |s, n| (s + k) % n) + 1
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1823_example_1() {
+        let n = 5;
+        let k = 2;
+
+        let result = 3;
+
+        assert_eq!(Solution::find_the_winner(n, k), result);
+    }
+
+    #[test]
+    fn test_1823_example_2() {
+        let n = 6;
+        let k = 5;
+
+        let result = 1;
+
+        assert_eq!(Solution::find_the_winner(n, k), result);
+    }
+}