Sync LeetCode submission - Count Nice Pairs in an Array (rust)

leetcode/problems/count_nice_pairs_in_an_array/solution.rs

@@ -0,0 +1,30 @@
+use std::collections::HashMap;
+impl Solution {
+    pub fn count_nice_pairs(nums: Vec<i32>) -> i32 {
+        const INF: i64 = 1000_000_007;
+        let rev = |mut x: i64| {
+            let mut ret: i64 = 0;
+            while x > 0 {
+                ret *= 10;
+                ret += x%10;
+                x /= 10;
+            }
+            return ret;
+        };
+        let mut delta_count: HashMap<i64, i64> = HashMap::new();
+        for x in nums {
+            let d = x as i64 - rev(x as i64);
+            *delta_count.entry(d).or_default() += 1;
+        }
+        //println!("{:?}", delta);
+        delta_count
+            .into_values()
+            .fold(0, |acc,n| {
+                if n < 2 {
+                    acc
+                } else {
+                    (acc + (n-1)*n/2)%INF
+                }
+            }) as i32
+    }
+}