2367. Number of Arithmetic Triplets: AC

Author: tan-wei

src/solution/mod.rs

@@ -1793,3 +1793,4 @@ mod s2363_merge_similar_items;
 mod s2364_count_number_of_bad_pairs;
 mod s2365_task_scheduler_ii;
 mod s2366_minimum_replacements_to_sort_the_array;
+mod s2367_number_of_arithmetic_triplets;

src/solution/s2367_number_of_arithmetic_triplets.rs

@@ -0,0 +1,81 @@
+/**
+ * [2367] Number of Arithmetic Triplets
+ *
+ * You are given a 0-indexed, strictly increasing integer array nums and a positive integer diff. A triplet (i, j, k) is an arithmetic triplet if the following conditions are met:
+ *
+ * 	i < j < k,
+ * 	nums[j] - nums[i] == diff, and
+ * 	nums[k] - nums[j] == diff.
+ *
+ * Return the number of unique arithmetic triplets.
+ *  
+ * Example 1:
+ *
+ * Input: nums = [0,1,4,6,7,10], diff = 3
+ * Output: 2
+ * Explanation:
+ * (1, 2, 4) is an arithmetic triplet because both 7 - 4 == 3 and 4 - 1 == 3.
+ * (2, 4, 5) is an arithmetic triplet because both 10 - 7 == 3 and 7 - 4 == 3.
+ *
+ * Example 2:
+ *
+ * Input: nums = [4,5,6,7,8,9], diff = 2
+ * Output: 2
+ * Explanation:
+ * (0, 2, 4) is an arithmetic triplet because both 8 - 6 == 2 and 6 - 4 == 2.
+ * (1, 3, 5) is an arithmetic triplet because both 9 - 7 == 2 and 7 - 5 == 2.
+ *
+ *  
+ * Constraints:
+ *
+ * 	3 <= nums.length <= 200
+ * 	0 <= nums[i] <= 200
+ * 	1 <= diff <= 50
+ * 	nums is strictly increasing.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/number-of-arithmetic-triplets/
+// discuss: https://leetcode.com/problems/number-of-arithmetic-triplets/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn arithmetic_triplets(nums: Vec<i32>, diff: i32) -> i32 {
+        nums.iter().fold(0, |acc, &x| {
+            if nums.contains(&(x + diff)) && nums.contains(&(x + diff * 2)) {
+                acc + 1
+            } else {
+                acc
+            }
+        })
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2367_example_1() {
+        let nums = vec![0, 1, 4, 6, 7, 10];
+        let diff = 3;
+
+        let result = 2;
+
+        assert_eq!(Solution::arithmetic_triplets(nums, diff), result);
+    }
+
+    #[test]
+    fn test_2367_example_2() {
+        let nums = vec![4, 5, 6, 7, 8, 9];
+        let diff = 2;
+
+        let result = 2;
+
+        assert_eq!(Solution::arithmetic_triplets(nums, diff), result);
+    }
+}