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  1. // #include <bits/stdc++.h>
  2. #include <iostream>
  3. #include <vector>
  4. #include <string>
  5. #include <map>
  6. #include <set>
  7. #include <cmath>
  8. #include <algorithm>
  9. #include <math.h>
  10. #include <iomanip>
  11. #include <iterator>
  12.  
  13. using namespace std;
  14.  
  15. #define PB push_back
  16. #define MP make_pair
  17. #define f first
  18. #define s second
  19. #define FOR(i,a,b) for (int i = a; i < b; ++i)
  20. #define RFOR(i, b, a) for (int i = b-1; i>=a; --i)
  21. #define FILL(a, b) memset(a, b, sizeof a)
  22. #define ALL(a) a.begin(), a.end()
  23. #define SZ(a) (int)a.size()
  24.  
  25. typedef long long LL;
  26. typedef pair<double, double> PII;
  27. typedef vector<int> VI;
  28. typedef vector<LL> VLL;
  29. typedef pair<LL, LL> PLL;
  30.  
  31. const int INF = 1000 * 1000 * 1000;
  32. const LL LINF = 1LL * INF * INF;
  33. const long double PI = acos(-1.);
  34. const double EPS = 1e-6;
  35. LL mod = INF + 7;
  36.  
  37. const int maxn = 3*100010;
  38. VI g[maxn];
  39. int d[maxn];
  40. int q[maxn];
  41. int main()
  42. {
  43. //  freopen("input.txt","r",stdin);
  44.     int n,m;
  45.     cin >> n >> m;
  46.     FOR(i,0,m)
  47.     {
  48.         int a,b;
  49.         cin >> a >> b;
  50.         a--;b--;
  51.         g[3*a].PB(3*b+1);
  52.         g[3*a+1].PB(3*b+2);
  53.         g[3*a+2].PB(3*b);
  54.     }
  55.     int s,t;
  56.     cin >> s >> t;
  57.     s--; t--;
  58.     FOR(i,0,maxn)
  59.         d[i] = INF;
  60.     d[3*s] = 0;
  61.     int qh = 0,qt = 0;
  62.     q[qh++] = 3*s;
  63.     while(qh!=qt)
  64.     {
  65.         int v = q[qt++];
  66.         FOR(i,0,SZ(g[v]))
  67.         {
  68.             if(d[g[v][i]]!=INF) continue;
  69.             q[qh++] = g[v][i];
  70.             d[g[v][i]] = d[v] + 1;    
  71.         }
  72.     }
  73.  
  74.  
  75.     if(d[3*t]==INF)
  76.     {
  77.         cout << -1;
  78.     }
  79.     else
  80.     {
  81.         cout << d[3*t]/3;
  82.     }
  83.  
  84.     return 0;
  85. }
Runtime error #stdin #stdout 0s 29760KB
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Standard input is empty
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Standard output is empty
https://ideone.com/QSR6CH
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
secret

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