2022-09-03：n 块石头放置在二维平面中的一些整数坐标点上 每个坐标点上最多只能有一块石头 如果一块石头的 同行或者同列 上有其他石头存在，那么就可以移除这块石头。 给你一个长度为 n 的数组

use std::collections::HashMap;fn main() {    let mut stones = vec![        vec![0, 0],        vec![0, 1],        vec![1, 0],        vec![1, 2],        vec![2, 1],        vec![2, 2],    ];    let ans = remove_stones(&mut stones);    println!("ans = {}", ans);}
fn remove_stones(stones: &mut Vec<Vec<i32>>) -> i32 {    let n = stones.len() as i32;    let mut row_pre: HashMap<i32, i32> = HashMap::new();    let mut col_pre: HashMap<i32, i32> = HashMap::new();    let mut uf = UnionFind::new(n);    for i in 0..n {        let x = stones[i as usize][0];        let y = stones[i as usize][1];        if !row_pre.contains_key(&x) {            row_pre.insert(x, i);        } else {            uf.union(i, *row_pre.get(&x).unwrap());        }        if !col_pre.contains_key(&y) {            col_pre.insert(y, i);        } else {            uf.union(i, *col_pre.get(&y).unwrap());        }    }    return n - uf.sets();}pub struct UnionFind {    father: Vec<i32>,    size: Vec<i32>,    help: Vec<i32>,    sets: i32,}impl UnionFind {    fn new(n: i32) -> UnionFind {        let mut father: Vec<i32> = vec![];        let mut size: Vec<i32> = vec![];        let mut help: Vec<i32> = vec![];        for i in 0..n {            father.push(i);            size.push(1);            help.push(0);        }        UnionFind {            father,            size,            help,            sets: n,        }    }
    fn union(&mut self, mut i: i32, mut j: i32) {        i = self.find(i);        j = self.find(j);        if i != j {            if self.size[i as usize] >= self.size[j as usize] {                self.father[j as usize] = i;                self.size[i as usize] += self.size[j as usize];            } else {                self.father[i as usize] = j;                self.size[j as usize] += self.size[i as usize];            }            self.sets -= 1;        }    }
    fn find(&mut self, mut i: i32) -> i32 {        let mut s = 0;        while i != self.father[i as usize] {            self.help[s] = i;            s += 1;            i = self.father[i as usize];        }        while s > 0 {            s -= 1;            self.father[self.help[s] as usize] = i;        }        return i;    }
    fn sets(&mut self) -> i32 {        self.sets    }}