Problem:
Score : 400 points

Problem Statement

There are N people standing on the x-axis.
Let the coordinate of Person i be x_i.
For every i, x_i is an integer between 0 and 10^9 (inclusive).
It is possible that more than one person is standing at the same coordinate.

You will given M pieces of information regarding the positions of these people.
The i-th piece of information has the form (L_i, R_i, D_i).
This means that Person R_i is to the right of Person L_i by D_i units of distance, that is, x_{R_i} - x_{L_i} = D_i holds.

It turns out that some of these M pieces of information may be incorrect.
Determine if there exists a set of values (x_1, x_2, ..., x_N) that is consistent with the given pieces of information.

Constraints

1 \leq N \leq 100 000

0 \leq M \leq 200 000

1 \leq L_i, R_i \leq N (1 \leq i \leq M)

0 \leq D_i \leq 10 000 (1 \leq i \leq M)

L_i \neq R_i (1 \leq i \leq M)

If i \neq j, then (L_i, R_i) \neq (L_j, R_j) and (L_i, R_i) \neq (R_j, L_j).

D_i are integers.

Input

Input is given from Standard Input in the following format:

N M
L_1 R_1 D_1
L_2 R_2 D_2
:
L_M R_M D_M

Output

If there exists a set of values (x_1, x_2, ..., x_N) that is consistent with all given pieces of information, print Yes; if it does not exist, print No.

Sample Input 1

3 3
1 2 1
2 3 1
1 3 2

Sample Output 1

Yes

Some possible sets of values (x_1, x_2, x_3) are (0, 1, 2) and (101, 102, 103).

Sample Input 2

3 3
1 2 1
2 3 1
1 3 5

Sample Output 2

No

If the first two pieces of information are correct, x_3 - x_1 = 2 holds, which is contradictory to the last piece of information.

Sample Input 3

4 3
2 1 1
2 3 5
3 4 2

Sample Output 3

Yes

Sample Input 4

10 3
8 7 100
7 9 100
9 8 100

Sample Output 4

No

Sample Input 5

100 0

Sample Output 5

Yes

Solution in Rust (1.15.1) (judge verdict: Time Limit Exceeded)

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::collections::HashMap;
use std::collections::HashSet;

#[derive(Copy, Clone)]
struct Edge {
    pub i: i32,
    pub dist: i32,
}
fn compute_distance(graph: &HashMap<i32, Vec<Edge>>, l: i32, r: i32) -> Option<i32> {
    let mut opened = HashSet::new();
    let mut queue: Vec<Vec<Edge>> = vec![];

    queue.push(vec![{ Edge { i: l, dist: 0 } }]);

    while let Some(e) = queue.pop() {
        let current = e[e.len() - 1];
        if current.i == r {
            let mut dist = 0;
            for i in e {
                dist = i.dist + dist;
            }
            return Some(dist);
        }
        if let Some(edges) = graph.get(&current.i) {
            for edge in edges {
                if opened.contains(&edge.i) {
                    continue;
                }
                let concat = [e.clone(), vec![{ edge.clone() }]].concat();
                queue.push(concat);
                opened.insert(edge.i);
            }
        }
    }
    return None;
}

fn main() {
    input!{
        n: i32,
        m: i32,
        lrd:[[i32;3];m]
    }

    let mut stat: HashMap<i32, Vec<Edge>> = HashMap::new();

    for c in lrd {
        let l = c[0] - 1;
        let r = c[1] - 1;
        let d = c[2];
        if let Some(distance) = compute_distance(&stat, l, r) {
            if distance != d {
                println!("No");
                std::process::exit(0);
            }
        }

        stat.entry(l).or_insert(vec![]).push(Edge { i: r, dist: d });
        stat.entry(r).or_insert(vec![]).push(Edge { i: l, dist: -d });
    }

    println!("Yes");
}