1539. Kth Missing Positive Number: AC

Author: tan-wei

src/solution/mod.rs

@@ -1160,3 +1160,4 @@ mod s1534_count_good_triplets;
 mod s1535_find_the_winner_of_an_array_game;
 mod s1536_minimum_swaps_to_arrange_a_binary_grid;
 mod s1537_get_the_maximum_score;
+mod s1539_kth_missing_positive_number;

src/solution/s1539_kth_missing_positive_number.rs

@@ -0,0 +1,75 @@
+/**
+ * [1539] Kth Missing Positive Number
+ *
+ * Given an array arr of positive integers sorted in a strictly increasing order, and an integer k.
+ * Return the k^th positive integer that is missing from this array.
+ *  
+ * Example 1:
+ *
+ * Input: arr = [2,3,4,7,11], k = 5
+ * Output: 9
+ * Explanation: The missing positive integers are [1,5,6,8,9,10,12,13,...]. The 5^th missing positive integer is 9.
+ *
+ * Example 2:
+ *
+ * Input: arr = [1,2,3,4], k = 2
+ * Output: 6
+ * Explanation: The missing positive integers are [5,6,7,...]. The 2^nd missing positive integer is 6.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= arr.length <= 1000
+ * 	1 <= arr[i] <= 1000
+ * 	1 <= k <= 1000
+ * 	arr[i] < arr[j] for 1 <= i < j <= arr.length
+ *
+ *  
+ * Follow up:
+ * Could you solve this problem in less than O(n) complexity?
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/kth-missing-positive-number/
+// discuss: https://leetcode.com/problems/kth-missing-positive-number/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn find_kth_positive(arr: Vec<i32>, k: i32) -> i32 {
+        arr.iter()
+            .enumerate()
+            .find(|(i, &val)| val - *i as i32 > k)
+            .unwrap_or((arr.len(), &0))
+            .0 as i32
+            + k
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1539_example_1() {
+        let arr = vec![2, 3, 4, 7, 11];
+        let k = 5;
+
+        let result = 9;
+
+        assert_eq!(Solution::find_kth_positive(arr, k), result);
+    }
+
+    #[test]
+    fn test_1539_example_2() {
+        let arr = vec![1, 2, 3, 4];
+        let k = 2;
+
+        let result = 6;
+
+        assert_eq!(Solution::find_kth_positive(arr, k), result);
+    }
+}