20240108 Finished

src/solution/mod.rs

@@ -13,3 +13,4 @@ mod s0006_zigzag_conversion;
 mod s0007_reverse_integer;
 mod s0004_median_of_two_sorted_arrays;
 mod s0743_network_delay_time;
+mod s0447_number_of_boomerangs;

src/solution/s0447_number_of_boomerangs.rs

@@ -0,0 +1,78 @@
+/**
+ * [447] Number of Boomerangs
+ *
+ * You are given n points in the plane that are all distinct, where points[i] = [xi, yi]. A boomerang is a tuple of points (i, j, k) such that the distance between i and j equals the distance between i and k (the order of the tuple matters).
+ * Return the number of boomerangs.
+ *  
+ * <strong class="example">Example 1:
+ * 
+ * Input: points = [[0,0],[1,0],[2,0]]
+ * Output: 2
+ * Explanation: The two boomerangs are [[1,0],[0,0],[2,0]] and [[1,0],[2,0],[0,0]].
+ * 
+ * <strong class="example">Example 2:
+ * 
+ * Input: points = [[1,1],[2,2],[3,3]]
+ * Output: 2
+ * 
+ * <strong class="example">Example 3:
+ * 
+ * Input: points = [[1,1]]
+ * Output: 0
+ * 
+ *  
+ * Constraints:
+ * 
+ * 	n == points.length
+ * 	1 <= n <= 500
+ * 	points[i].length == 2
+ * 	-10^4 <= xi, yi <= 10^4
+ * 	All the points are unique.
+ * 
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.cn/problems/number-of-boomerangs/
+// discuss: https://leetcode.cn/problems/number-of-boomerangs/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+use std::collections::HashMap;
+impl Solution {
+    pub fn number_of_boomerangs(points: Vec<Vec<i32>>) -> i32 {
+        let mut result = 0;
+
+        for p in &points {
+            let mut values = HashMap::new();
+
+            for q in &points {
+                let dis = (p[0] - q[0]).pow(2) + (p[1] - q[1]).pow(2);
+
+                let c = values.entry(dis).or_insert(0);
+                *c += 1;
+            }
+
+            for (_, v) in &values {
+                // 实际上并不需要，因为最小值为1
+                // 计算的结果为0
+                if  *v >= 2 {
+                    // result += A_m^2
+                    result += (*v) * (*v - 1);
+                }
+            }
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_447() {
+    }
+}