Created
November 3, 2017 14:27
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DDCC2017 Final C
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#include <iostream> | |
#include <iomanip> | |
#include <vector> | |
#include <algorithm> | |
#include <numeric> | |
#include <functional> | |
#include <cmath> | |
#include <queue> | |
#include <stack> | |
#include <set> | |
#include <map> | |
#include <sstream> | |
#include <string> | |
#define _repargs(_1,_2,_3,name,...) name | |
#define _rep(i,n) repi(i,0,n) | |
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);++i) | |
#define rep(...) _repargs(__VA_ARGS__,repi,_rep,)(__VA_ARGS__) | |
#define all(x) (x).begin(),(x).end() | |
#define mod 1000000007 | |
#define mp make_pair | |
#define pb push_back | |
typedef long long ll; | |
using namespace std; | |
template <typename T> | |
inline void output(T a, int p = 0) { | |
if(p) cout << fixed << setprecision(p) << a << "\n"; | |
else cout << a << "\n"; | |
} | |
// end of template | |
ll inf = 1LL << 61; | |
struct node {int to; ll cost;}; | |
vector<vector<node>> G; | |
vector<vector<node>> rG; | |
vector<ll> dist; | |
int to = 0; | |
bool ok = true; | |
void dfs(int cur) { | |
for(node n: G[cur]) { | |
if(to == n.to) continue; | |
if(dist[n.to] == inf) { | |
dist[n.to] = dist[cur] + n.cost; | |
dfs(n.to); | |
} | |
else { | |
if(dist[n.to] != dist[cur] + n.cost) ok = false; | |
} | |
} | |
} | |
int main() { | |
cin.tie(0); | |
ios::sync_with_stdio(0); | |
// source code | |
int N, M; | |
cin >> N >> M; | |
G.resize(N); | |
rG.resize(N); | |
rep(i, M) { | |
int a, b; | |
ll c; | |
cin >> a >> b >> c; | |
a--; | |
b--; | |
G[a].pb({b, c}); | |
rG[b].pb({a, c}); | |
} | |
rep(i, N) { | |
dist.assign(N, inf); | |
dist[i] = 0; | |
ok = true; | |
to = i; | |
dfs(i); | |
if(ok) { | |
int cnt = 0; | |
for (node n: rG[i]) { | |
if(dist[n.to] + n.cost != 0) cnt++; | |
} | |
if(cnt <= 1) { | |
output("Yes"); | |
return 0; | |
} | |
} | |
} | |
output("No"); | |
return 0; | |
} |
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