1608. Special Array With X Elements Greater Than or Equal X: AC

Author: tan-wei

src/solution/mod.rs

@@ -1212,3 +1212,4 @@ mod s1603_design_parking_system;
 mod s1604_alert_using_same_key_card_three_or_more_times_in_a_one_hour_period;
 mod s1605_find_valid_matrix_given_row_and_column_sums;
 mod s1606_find_servers_that_handled_most_number_of_requests;
+mod s1608_special_array_with_x_elements_greater_than_or_equal_x;

src/solution/s1608_special_array_with_x_elements_greater_than_or_equal_x.rs

@@ -0,0 +1,82 @@
+/**
+ * [1608] Special Array With X Elements Greater Than or Equal X
+ *
+ * You are given an array nums of non-negative integers. nums is considered special if there exists a number x such that there are exactly x numbers in nums that are greater than or equal to x.
+ * Notice that x does not have to be an element in nums.
+ * Return x if the array is special, otherwise, return -1. It can be proven that if nums is special, the value for x is unique.
+ *  
+ * Example 1:
+ *
+ * Input: nums = [3,5]
+ * Output: 2
+ * Explanation: There are 2 values (3 and 5) that are greater than or equal to 2.
+ *
+ * Example 2:
+ *
+ * Input: nums = [0,0]
+ * Output: -1
+ * Explanation: No numbers fit the criteria for x.
+ * If x = 0, there should be 0 numbers >= x, but there are 2.
+ * If x = 1, there should be 1 number >= x, but there are 0.
+ * If x = 2, there should be 2 numbers >= x, but there are 0.
+ * x cannot be greater since there are only 2 numbers in nums.
+ *
+ * Example 3:
+ *
+ * Input: nums = [0,4,3,0,4]
+ * Output: 3
+ * Explanation: There are 3 values that are greater than or equal to 3.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= nums.length <= 100
+ * 	0 <= nums[i] <= 1000
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/special-array-with-x-elements-greater-than-or-equal-x/
+// discuss: https://leetcode.com/problems/special-array-with-x-elements-greater-than-or-equal-x/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn special_array(nums: Vec<i32>) -> i32 {
+        let mut nums = nums;
+
+        nums.sort_unstable();
+        let n = nums.len() as i32;
+
+        for i in 0..n + 1 {
+            let (mut lo, mut hi) = (0 as i32, (n - 1) as i32);
+            let x = i as i32;
+            let mut i_idx = -1;
+
+            while lo <= hi {
+                let mi = lo + (hi - lo) / 2;
+                if nums[mi as usize] >= x {
+                    i_idx = mi;
+                    hi = mi - 1;
+                } else {
+                    lo = mi + 1;
+                }
+            }
+            if x == n - i_idx {
+                return x;
+            }
+        }
+
+        -1
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1608_example_1() {}
+}