How many directions you need to change the graph to go












3















There is a directed graph. All edges are in one direction only. The problem is to find the minimum number of possible changes so that you can get from one given node to another.



For example:
For a graph with three nodes and two edges (1->2, 3->2). You need to determine how many changes in edge direction should be made to achieve a path from node 1 to node 3. The answer will be 1, since it is enough to change edge 2->3 and get the path 1->2->3.



This is a task with a limited time (5s). The number of points and edges are in the range [1,10^6]. Memory is limited to 256 megabytes



Please help with finding a fast algorithm to solve this task






algorithm graph







share|improve this question




















  • 2





    What have you tried so far?

    – merlyn
    Jan 2 at 15:05






  • 7





    Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

    – Nico Schertler
    Jan 2 at 15:06
















3















There is a directed graph. All edges are in one direction only. The problem is to find the minimum number of possible changes so that you can get from one given node to another.



For example:
For a graph with three nodes and two edges (1->2, 3->2). You need to determine how many changes in edge direction should be made to achieve a path from node 1 to node 3. The answer will be 1, since it is enough to change edge 2->3 and get the path 1->2->3.



This is a task with a limited time (5s). The number of points and edges are in the range [1,10^6]. Memory is limited to 256 megabytes



Please help with finding a fast algorithm to solve this task






algorithm graph







share|improve this question




















  • 2





    What have you tried so far?

    – merlyn
    Jan 2 at 15:05






  • 7





    Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

    – Nico Schertler
    Jan 2 at 15:06














3












3








3








There is a directed graph. All edges are in one direction only. The problem is to find the minimum number of possible changes so that you can get from one given node to another.



For example:
For a graph with three nodes and two edges (1->2, 3->2). You need to determine how many changes in edge direction should be made to achieve a path from node 1 to node 3. The answer will be 1, since it is enough to change edge 2->3 and get the path 1->2->3.



This is a task with a limited time (5s). The number of points and edges are in the range [1,10^6]. Memory is limited to 256 megabytes



Please help with finding a fast algorithm to solve this task






algorithm graph







share|improve this question
















There is a directed graph. All edges are in one direction only. The problem is to find the minimum number of possible changes so that you can get from one given node to another.



For example:
For a graph with three nodes and two edges (1->2, 3->2). You need to determine how many changes in edge direction should be made to achieve a path from node 1 to node 3. The answer will be 1, since it is enough to change edge 2->3 and get the path 1->2->3.



This is a task with a limited time (5s). The number of points and edges are in the range [1,10^6]. Memory is limited to 256 megabytes



Please help with finding a fast algorithm to solve this task






algorithm graph




algorithm graph






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Jan 2 at 22:32









zohar.kom

1,0841720




1,0841720










asked Jan 2 at 14:42









alex zamyatinalex zamyatin

316




316








  • 2





    What have you tried so far?

    – merlyn
    Jan 2 at 15:05






  • 7





    Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

    – Nico Schertler
    Jan 2 at 15:06














  • 2





    What have you tried so far?

    – merlyn
    Jan 2 at 15:05






  • 7





    Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

    – Nico Schertler
    Jan 2 at 15:06








2




2





What have you tried so far?

– merlyn
Jan 2 at 15:05





What have you tried so far?

– merlyn
Jan 2 at 15:05




7




7





Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

– Nico Schertler
Jan 2 at 15:06





Mininun changes required in a directed graph to make path from 1 to n, Minimum edges to reverse to make path from a source to a destination

– Nico Schertler
Jan 2 at 15:06












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