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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

/*
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 */
import javax.naming.OperationNotSupportedException;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.nio.file.Path;
import java.util.*;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.lang.Math.max;
import static java.lang.Math.min;
import static java.lang.Math.pow;
import static java.lang.Math.abs;

import static java.lang.String.format;


public class Main {
    final static int INF = Integer.MAX_VALUE>>1;
    final static int MOD = 1_000_000_007;
    final static int[] dx4 = { 0, 1, 0, -1 };
    final static int[] dy4 = { 1, 0, -1, 0 };
    final static int[] dx8 = {0, 1, 1,  1,  0, -1, -1, -1};
    final static int[] dy8 = {1, 1, 0, -1, -1, -1, 0, 1};
    public static void main(String[] args) throws Exception{
        Scanner sc=new Scanner();
        int n=sc.nextInt();
        int m=sc.nextInt();
        if(m==0){
            put("Yes");
            return;
        }
        int[] from = new int[m];
        int[] to = new int[m];
        int[] dist = new int[m];
        for (int i = 0; i < m; i++) {
            from[i]=sc.nextInt()-1;
            to[i]=sc.nextInt()-1;
            dist[i]=sc.nextInt();
        }
        Map<Integer,List<LGraph.Edge>> graph=LGraph.makeLGraph(from,to,dist);
        long[] pos = new long[n];
        Arrays.fill(pos,Long.MAX_VALUE);
        for (int i = 0; i < n; i++) {
            if(pos[from[i]]==Long.MAX_VALUE){
                Deque<Integer> deq = new ArrayDeque<>();
                deq.add(from[i]);
                pos[from[i]]=0;
                while (deq.size() > 0) {
                    int node= deq.removeFirst();
                    for (LGraph.Edge e : graph.get(node)) {
                        if(pos[e.to]==Long.MAX_VALUE){
                            pos[e.to] = pos[node] + e.weight;
                            deq.addLast(e.to);
                        }else{
                            if(pos[e.to]!=pos[node]+e.weight){
                                put("No");
                                return;
                            }
                        }
                    }
                }
            }
        }
        put("Yes");





    }
    final private static class LGraph{
        final public static class Edge{
            private int to,weight;
            protected Edge(int to, int weight) {
                this.to=to;
                this.weight=weight;
            }

            public int getTo() {
                return to;
            }

            public int getWeight() {
                return weight;
            }
        }
        public static Map<Integer,List<Edge>> makeLGraph(int[] from,int[] to,int[] dist){
            if(from.length!=to.length||to.length!=dist.length){
                throw new IllegalArgumentException();
            }
            Map<Integer, List<Edge>> g = new HashMap<>();
            int m= from.length;
            for (int i = 0; i < m; i++) {
                List<Edge> list=g.getOrDefault(from[i],new ArrayList<>(1));
                list.add(new Edge(to[i],dist[i]));
                g.put(from[i],list);
                list = g.getOrDefault(to[i], new ArrayList<>(1));
                list.add(new Edge(from[i], -dist[i]));
                g.put(to[i],list);
            }
            return g;
        }
        public static Map<Integer,List<Edge>> makeLGraph(int[] from,int[] to){
            if(from.length!=to.length){
                throw new IllegalArgumentException();
            }
            int[] dist = new int[from.length];
            Arrays.fill(dist,0);
            return makeLGraph(from,to,dist);
        }
    }


    public static void print(Object object){
        System.out.print(object);
    }
    public static void put(Object object) {
        System.out.println(object);
    }
    public static void put(){
        System.out.println();
    }

    public static void printE(Object object){
        System.err.print("DEBUG:"+object);
    }
    public static void putE(Object object){
        System.err.println("DEBUG:"+object);
    }
    public static void putE(){
        System.err.println("DEBUG:");
    }

    public static void print(String format,Object... args){
        System.out.print(String.format(format,args));
    }
    public static void put(String format,Object... args) {
        System.out.println(String.format(format,args));
    }
    public static void printE(String format,Object... args){
        System.err.print("DEBUG:"+String.format(format,args));
    }
    public static void putE(String format,Object... args){
        System.err.println("DEBUG:"+String.format(format,args));
    }

    final static private class Scanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
    final static private class FixedIntPair {
        final public int x, y;
        final static public FixedIntPair ZEROS=new FixedIntPair(0,0);
        FixedIntPair(int x, int y) {
            this.x = x;
            this.y = y;
        }
        public static double distance(FixedIntPair fip1,FixedIntPair fip2){
            double x = (double) fip1.x - fip2.x;
            double y = (double) fip1.y - fip2.y;
            return Math.sqrt(x*x+y*y);
        }

        @Override
        public int hashCode() {
            return x+y;
        }

        @Override
        public boolean equals(Object obj) {
            boolean result=super.equals(obj);
            if(obj.getClass()!=this.getClass()){
                return false;
            }
            FixedIntPair pair=(FixedIntPair) obj;
            if(this.x==pair.x&&this.y==pair.y) return true;
            return false;
        }

        @Override
        public String toString() {
            return String.format(FixedIntPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class FixedLongPair {
        final public long x, y;
        final static public FixedLongPair ZEROS=new FixedLongPair(0,0);
        FixedLongPair(long x, long y) {
            this.x = x;
            this.y = y;
        }
        public static double distance(FixedLongPair flp1,FixedLongPair flp2){
            double x = (double) flp1.x - flp2.x;
            double y = (double) flp1.y - flp2.y;
            return Math.sqrt(x*x+y*y);
        }

        @Override
        public int hashCode() {
            return (int)x+(int)y;
        }

        @Override
        public boolean equals(Object obj) {
            boolean result=super.equals(obj);
            if(obj.getClass()!=this.getClass()){
                return false;
            }
            FixedLongPair pair=(FixedLongPair)obj;
            if(this.x==pair.x&&this.y==pair.y) return true;
            return false;
        }

        @Override
        public String toString() {
            return String.format(FixedLongPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class Binary{
        public static String toZeroPadding(int i){
            return String.format("%"+Integer.toBinaryString(-1).length()+"s",Integer.toBinaryString(i)).replace(' ','0');
        }
        public static String toZeroPadding(long i){
            return String.format("%"+Long.toBinaryString(-1).length()+"s",Long.toBinaryString(i)).replace(' ','0');
        }
    }

    final static private class Util {
        static long gcd(long a,long b){
            //最大公約数　
            if(a%b==0)return b;
            return gcd(b,a%b);
        }
        static long lcm(long a,long b){
            //最小公倍数
            long gcd=gcd(a,b);
            long result=b/gcd;
            return a*result;
        }
        static <T extends Comparable<T>> Map<T,Integer> count(List<T> list){
            //副作用
            Collections.sort(list);
            Map<T,Integer> result=new HashMap<>();
            int l=0,r=0;
            while(l<list.size()){
                while(r<list.size()-1&&list.get(r).equals(r+1)){
                    r++;
                }
                result.put(list.get(r),r-l+1);
                r++;
                l=r;
            }
            return result;

        }
        static Map<Integer,Integer> count(int[] array){
            //副作用
            Arrays.sort(array);
            Map<Integer,Integer> result=new HashMap<>();
            int l=0,r=0;
            while(l<array.length){
                while(r<array.length-1&&array[r]==array[r+1]){
                    r++;
                }
                result.put(array[l],r-l+1);
                r++;
                l=r;
            }
            return result;
        }
        static <T> String toStringBWS(Iterable<T> iterable){
            Iterator<T> ite=iterable.iterator();
            return toStringBWS(ite);
        }
        static <T> String toStringBWS(Iterator<T> ite){
            StringBuilder sb=new StringBuilder();
            sb.append(ite.next());
            while(ite.hasNext()){
                sb.append(" ");
                sb.append(ite.next());
            }
            return sb.toString();
        }
        static long factoringInPrimeNumbers(long n,int[] a){
            //素因数分解
            for(int i=2;n>1&&i< a.length;i++){
                while(n%i==0){
                    a[i]++;
                    n/=i;
                }
            }
            return n;

        }
        static boolean isValidCell(int i,int j,int h,int w){
            return i>=0&&i<h&&j>=0&&j<w;
        }
    }
}