20250412 finished.

src/problem/mod.rs

@@ -593,3 +593,5 @@ mod p2999_count_the_number_of_powerful_integers;
 mod p3375_minimum_operations_to_make_array_values_equal_to_k;
 
 mod p2843_count_symmetric_integers;
+
+mod p3272_find_the_count_of_good_integers;

src/problem/p3272_find_the_count_of_good_integers.rs

@@ -0,0 +1,81 @@
+/**
+ * [3272] Find the Count of Good Integers
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashSet;
+
+impl Solution {
+    pub fn count_good_integers(n: i32, k: i32) -> i64 {
+        let n = n as usize;
+        let k = k as i64;
+        let base_value = 10i64.pow((n as u32 - 1) / 2);
+        let length = (n + 1) / 2;
+        let mut dict = HashSet::new();
+
+        // 枚举n个数位的回文数
+        for mut i in base_value..base_value * 10 {
+            let mut s = Vec::with_capacity(length);
+
+            while i != 0 {
+                s.push(i % 10);
+                i = i / 10;
+            }
+
+            // 这里拼接回文字符串有点困难
+            // 因为上面存数字字符存的是倒序
+            // 即 123 -> 3 2 1
+            // 所以 12321 -> 1 2 3 2 1
+            let mut real_str: Vec<i64> = s
+                .iter()
+                .rev()
+                .chain(s.iter().skip(n & 1))
+                .map(|x| *x)
+                .collect();
+
+            let number = real_str.iter().fold(0, |v, i| v * 10 + *i);
+            if number % k == 0 {
+                real_str.sort_unstable();
+                dict.insert(real_str);
+            }
+        }
+
+        let mut factorial = Vec::with_capacity(n + 1);
+        factorial.push(1);
+        for i in 1..=n {
+            factorial.push(factorial[i - 1] * i as i64);
+        }
+
+        let mut result = 0;
+
+        for str in dict.into_iter() {
+            let mut counts = [0; 10];
+            for i in str {
+                counts[i as usize] += 1;
+            }
+
+            let mut total = (n - counts[0]) as i64 * factorial[n - 1];
+            for x in counts {
+                total /= factorial[x]
+            }
+            result += total;
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_3272() {
+        assert_eq!(27, Solution::count_good_integers(3, 5));
+        assert_eq!(2, Solution::count_good_integers(1, 4));
+        assert_eq!(2468, Solution::count_good_integers(5, 6));
+    }
+}