20250425 finished.

src/problem/mod.rs

@@ -616,3 +616,5 @@ mod p2145_count_the_hidden_sequences;
 
 mod p1399_count_largest_group;
 mod p2338_count_the_number_of_ideal_arrays;
+
+mod p2845_count_of_interesting_subarrays;

src/problem/p2845_count_of_interesting_subarrays.rs

@@ -0,0 +1,53 @@
+/**
+ * [2845] Count of Interesting Subarrays
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn count_interesting_subarrays(nums: Vec<i32>, modulo: i32, k: i32) -> i64 {
+        let n = nums.len();
+        let mut count = vec![0; n + 1];
+        for (i, &v) in nums.iter().enumerate() {
+            count[i + 1] = count[i] + if v % modulo == k { 1 } else { 0 };
+        }
+
+        let mut map = HashMap::new();
+        let mut result = 0;
+
+        // 类似于两数之和
+        for i in 0..=n {
+            let target = (count[i] + modulo - k) % modulo;
+
+            if let Some(&v) = map.get(&target) {
+                result += v;
+            }
+
+            let entry = map.entry(count[i] % modulo).or_insert(0);
+            *entry += 1;
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2845() {
+        assert_eq!(
+            3,
+            Solution::count_interesting_subarrays(vec![3, 2, 4], 2, 1)
+        );
+        assert_eq!(
+            2,
+            Solution::count_interesting_subarrays(vec![3, 1, 9, 6], 3, 0)
+        );
+    }
+}