add: 回旋镖的数量

README.md

@@ -161,6 +161,10 @@ Rust标准库`std::collections`提供了4种通用容器类型，包含一下8
 
 ### 数组/队列/集合/映射
 
+- [回旋镖的数量](src/array/number_of_boomerangs.rs)  [数组, 哈希表, 数学]
+
+  - LeetCode 447. 回旋镖的数量 <https://leetcode.cn/problems/number-of-boomerangs>
+
 - [经营摩天轮的最大利润](src/array/maximum_profit_of_operating_a_centennial_wheel.rs)  [数组, 模拟]
 
   - LeetCode 1599. 经营摩天轮的最大利润 <https://leetcode.cn/problems/maximum-profit-of-operating-a-centennial-wheel>

src/array/mod.rs

@@ -53,3 +53,4 @@ pub mod house_robber;
 pub mod stamping_the_grid;
 pub mod min_cost_climbing_stairs;
 pub mod maximum_profit_of_operating_a_centennial_wheel;
+pub mod number_of_boomerangs;

src/array/number_of_boomerangs.rs

@@ -0,0 +1,28 @@
+// 回旋镖的数量
+// https://leetcode.cn/problems/number-of-boomerangs
+// INLINE  ../../images/array/number_of_boomerangs.jpeg
+
+pub struct Solution;
+
+impl Solution {
+    fn distance(p1: &Vec<i32>, p2: &Vec<i32>) -> i32 {
+        (p1[0] - p2[0]).pow(2) + (p1[1] - p2[1]).pow(2)
+    }
+    pub fn number_of_boomerangs(points: Vec<Vec<i32>>) -> i32 {
+        let mut res = 0;
+        for i in 0..points.len() {
+            let mut map = std::collections::HashMap::new();
+            for j in 0..points.len() {
+                if i != j {
+                    let distance = Solution::distance(&points[i], &points[j]);
+                    let count = map.entry(distance).or_insert(0);
+                    *count += 1;
+                }
+            }
+            for (_, v) in map {
+                res += v * (v - 1);
+            }
+        }
+        res
+    }
+}

tests/array/mod.rs

@@ -53,3 +53,4 @@ pub mod house_robber_test;
 pub mod stamping_the_grid_test;
 pub mod min_cost_climbing_stairs_test;
 pub mod maximum_profit_of_operating_a_centennial_wheel_test;
+pub mod number_of_boomerangs_test;

tests/array/number_of_boomerangs_test.rs

@@ -0,0 +1,23 @@
+use rust_practice::array::number_of_boomerangs::Solution;
+
+#[test]
+fn number_of_boomerangs() {
+    // 示例 1：
+    // 输入：points = [[0,0],[1,0],[2,0]]
+    // 输出：2
+    // 解释：两个回旋镖为 [[1,0],[0,0],[2,0]] 和 [[1,0],[2,0],[0,0]]
+    let points = vec![vec![0, 0], vec![1, 0], vec![2, 0]];
+    assert_eq!(Solution::number_of_boomerangs(points), 2);
+
+    // 示例 2：
+    // 输入：points = [[1,1],[2,2],[3,3]]
+    // 输出：2
+    let points = vec![vec![1, 1], vec![2, 2], vec![3, 3]];
+    assert_eq!(Solution::number_of_boomerangs(points), 2);
+
+    // 示例 3：
+    // 输入：points = [[1,1]]
+    // 输出：0
+    let points = vec![vec![1, 1]];
+    assert_eq!(Solution::number_of_boomerangs(points), 0);
+}