Add problem 3159: Find Occurrences of an Element in an Array

Author: EFanZh

src/lib.rs

@@ -2112,6 +2112,7 @@ pub mod problem_3151_special_array_i;
 pub mod problem_3152_special_array_ii;
 pub mod problem_3153_sum_of_digit_differences_of_all_pairs;
 pub mod problem_3158_find_the_xor_of_numbers_which_appear_twice;
+pub mod problem_3159_find_occurrences_of_an_element_in_an_array;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3159_find_occurrences_of_an_element_in_an_array/iterative.rs

@@ -0,0 +1,41 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn occurrences_of_element(nums: Vec<i32>, queries: Vec<i32>, x: i32) -> Vec<i32> {
+        let mut nums = nums;
+        let nums = &mut *nums;
+        let mut count = 0;
+
+        for i in 0..nums.len() {
+            if nums[i] == x {
+                nums[count] = i as _;
+                count += 1;
+            }
+        }
+
+        let indices = &mut nums[..count];
+
+        queries
+            .into_iter()
+            .map(|i| indices.get(i.cast_unsigned() as usize - 1).copied().unwrap_or(-1))
+            .collect()
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn occurrences_of_element(nums: Vec<i32>, queries: Vec<i32>, x: i32) -> Vec<i32> {
+        Self::occurrences_of_element(nums, queries, x)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3159_find_occurrences_of_an_element_in_an_array/mod.rs

@@ -0,0 +1,24 @@
+pub mod iterative;
+
+pub trait Solution {
+    fn occurrences_of_element(nums: Vec<i32>, queries: Vec<i32>, x: i32) -> Vec<i32>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (
+                (&[1, 3, 1, 7] as &[_], &[1, 3, 2, 4] as &[_], 1),
+                &[0, -1, 2, -1] as &[_],
+            ),
+            ((&[1, 2, 3], &[10], 5), &[-1]),
+        ];
+
+        for ((nums, queries, x), expected) in test_cases {
+            assert_eq!(S::occurrences_of_element(nums.to_vec(), queries.to_vec(), x), expected);
+        }
+    }
+}