20241227 finished.

src/problem/mod.rs

@@ -394,3 +394,5 @@ mod p1705_maximum_number_of_eaten_apples;
 mod p3218_minimum_cost_for_cutting_cake_i;
 
 mod p3083_existence_of_a_substring_in_a_string_and_its_reverse;
+
+mod p3159_find_occurrences_of_an_element_in_an_array;

src/problem/p3159_find_occurrences_of_an_element_in_an_array.rs

@@ -0,0 +1,49 @@
+/**
+ * [3159] Find Occurrences of an Element in an Array
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn occurrences_of_element(nums: Vec<i32>, queries: Vec<i32>, x: i32) -> Vec<i32> {
+        let x_pos: Vec<usize> = nums
+            .iter()
+            .enumerate()
+            .filter_map(|(i, v)| if *v == x { Some(i) } else { None })
+            .collect();
+
+        let result = queries
+            .into_iter()
+            .map(|x| {
+                let x = x as usize - 1;
+                if x >= x_pos.len() {
+                    -1
+                } else {
+                    x_pos[x] as i32
+                }
+            })
+            .collect();
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3159() {
+        assert_eq!(
+            vec![0, -1, 2, -1],
+            Solution::occurrences_of_element(vec![1, 3, 1, 7], vec![1, 3, 2, 4], 1)
+        );
+        assert_eq!(
+            vec![-1],
+            Solution::occurrences_of_element(vec![1, 2, 3], vec![10], 5)
+        );
+    }
+}