Problem:
Score : 500 points

Problem Statement

There are N cards placed face down in a row. On each card, an integer 1 or 2 is written.

Let A_i be the integer written on the i-th card.

Your objective is to guess A_1, A_2, ..., A_N correctly.

You know the following facts:

For each i = 1, 2, ..., M, the value A_{X_i} + A_{Y_i} + Z_i is an even number.

You are a magician and can use the following magic any number of times:

Magic: Choose one card and know the integer A_i written on it. The cost of using this magic is 1.

What is the minimum cost required to determine all of A_1, A_2, ..., A_N?

It is guaranteed that there is no contradiction in given input.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq X_i < Y_i \leq N

1 \leq Z_i \leq 100

The pairs (X_i, Y_i) are distinct.

There is no contradiction in input. (That is, there exist integers A_1, A_2, ..., A_N that satisfy the conditions.)

Input

Input is given from Standard Input in the following format:

N M
X_1 Y_1 Z_1
X_2 Y_2 Z_2
\vdots
X_M Y_M Z_M

Output

Print the minimum total cost required to determine all of A_1, A_2, ..., A_N.

Sample Input 1

3 1
1 2 1

Sample Output 1

2

You can determine all of A_1, A_2, A_3 by using the magic for the first and third cards.

Sample Input 2

6 5
1 2 1
2 3 2
1 3 3
4 5 4
5 6 5

Sample Output 2

2

Sample Input 3

100000 1
1 100000 100

Sample Output 3

99999

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

// reference: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let mut s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };

    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };

    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };

    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

use std::cmp::Ordering;
#[derive(Eq, PartialEq, Clone, Debug)]
pub struct Rev<T>(pub T);

impl<T: PartialOrd> PartialOrd for Rev<T> {
    fn partial_cmp(&self, other: &Rev<T>) -> Option<Ordering> {
        other.0.partial_cmp(&self.0)
    }
}

impl<T: Ord> Ord for Rev<T> {
    fn cmp(&self, other: &Rev<T>) -> Ordering {
        other.0.cmp(&self.0)
    }
}

impl<T: Copy> Copy for Rev<T> {}

struct UnionFind {
    data: Vec<usize>,
    size: Vec<usize>,
    groupes: usize,
}

impl UnionFind {
    fn new(n: usize) -> UnionFind {
        let mut data = vec![0; n];
        for i in 0..data.len() {
            data[i] = i;
        }
        let mut size = vec![1; n];
        UnionFind {
            data: data,
            size: size,
            groupes: n,
        }
    }

    fn unite(&mut self, a: usize, b: usize) {
        let mut a = self.find(a);
        let mut b = self.find(b);
        if a == b {
            return;
        }

        if self.size[a] < self.size[b] {
            std::mem::swap(&mut a, &mut b);
        }

        self.groupes -= 1;
        self.size[a] += self.size[b];
        self.data[b] = a;
    }

    fn find(&mut self, x: usize) -> usize {
        let t = self.data[x];
        if t != x {
            let p = self.find(t);
            self.data[x] = p;
        }
        self.data[x]
    }
}

use std::collections::HashSet;

fn main() {
    input! {
        n: usize, m: usize,
        xyz: [(usize1, usize1, usize); m]
    }

    let mut uf = UnionFind::new(n);
    let mut diff = Vec::new();
    for (x, y, z) in xyz {
        if z % 2 == 0 {
            uf.unite(x, y);
        } else {
            diff.push((x, y));
        }
    }

    let ds = diff
        .into_iter()
        .map(|(x, y)| {
            let x = uf.find(x);
            let y = uf.find(y);
            if x <= y {
                (x, y)
            } else {
                (y, x)
            }
        })
        .collect::<HashSet<_>>();

    let ans = uf.groupes - ds.len();
    println!("{}", ans);
}