docs: add problem description for 973 leetcode

Author: bujosa

src/medium/readme.md

@@ -1427,6 +1427,41 @@ Put the code below in main.rs and run `cargo run`
   println!("result: {}", result);
 ```
 
+# 973. K Closest Points to Origin
+
+## Description
+
+We have a list of points on the plane. Find the K closest points to the origin (0, 0).
+
+(Here, the distance between two points on a plane is the Euclidean distance.)
+
+You may return the answer in any order. The answer is guaranteed to be unique (except for the order that it is in.)
+
+## Examples
+
+```text
+Input: points = [[1,3],[-2,2]], K = 1
+Output: [[-2,2]]
+
+Explanation:
+The distance between (1, 3) and the origin is sqrt(10).
+The distance between (-2, 2) and the origin is sqrt(8).
+
+Since sqrt(8) < sqrt(10), (-2, 2) is closer to the origin.
+We only want the closest K = 1 points from the origin, so the answer is just [[-2,2]].
+```
+
+## How to Run in main.rs
+
+Put the code below in main.rs and run `cargo run`
+
+```rust
+  let points = vec![vec![1, 3], vec![-2, 2]];
+  let k = 1;
+  let result = leetcode::medium::k_closest_points_to_origin::k_closest(points, k);
+  println!("result: {:?}", result);
+```
+
 # 981. Time Based Key-Value Store
 
 ## Description

src/readme.md

@@ -87,6 +87,7 @@
   - [x] [739. Daily temperatures](../src/medium/daily_temperatures.rs) -> [Problem Description](../src/medium/readme.md#739-daily-temperatures)
   - [x] [853. Car fleet](../src/medium/car_fleet.rs) -> [Problem Description](../src/medium/readme.md#853-car-fleet)
   - [x] [875. Koko eating bananas](../src/medium/koko_eating_bananas.rs) -> [Problem Description](../src/medium/readme.md#875-koko-eating-bananas)
+  - [ ] [973. K closest points to origin](../src/medium/k_closest_points_to_origin.rs) -> [Problem Description](../src/medium/readme.md#973-k-closest-points-to-origin)
   - [x] [981. Time based key-value store](../src/medium/time_based_key_value_store.rs) -> [Problem Description](../src/medium/readme.md#981-time-based-key-value-store)
   - [x] [1448. Count good nodes in binary tree](../src/medium/count_good_nodes_in_binary_tree.rs) -> [Problem Description](../src/medium/readme.md#1448-count-good-nodes-in-binary-tree)
 - [Hard](../src/hard)