# `transpose_graph`

    template <class VertexListGraph, class MutableGraph>
    void transpose_graph(const VertexListGraph& G, MutableGraph& G_T,
        const bgl_named_params<P, T, R>& params = all defaults)

This function computes the transpose of a directed graph. The transpose of a directed graph G = (V, E)is the graph GT = (V, ET) , where ET = {(v, u) in V x V: (u, v) in E} . i.e., GT is G with all its edges reversed. Graph `G_T` passed into the algorithm must have no vertices and no edges. The vertices and edges will be added by `transpose_graph()` by calling `add_vertex` and `add_edge` as follows for each edge (u,v) in `G`.

### Example

Here's an example of transposing a graph: `example/transpose-example.cpp`.

### Where Defined

`boost/graph/transpose_graph.hpp`

### Parameters

IN: `const VertexListGraph& G`

> A directed graph. The graph type must be a model of Vertex List Graph.

OUT: `const MutableGraph& G_T`

> The transposed graph. The graph type must be a model of Mutable Graph.

### Named Parameters

IN: `vertex_copy(VertexCopier vc)`

> This is a Binary Function that copies the properties of a vertex in the original graph into the corresponding vertex in the copy.
> Default: `vertex_copier<VertexListGraph, MutableGraph>` which uses the property tag `vertex_all` to access a property map from the graph.

IN: `edge_copy(EdgeCopier ec)`

> This is a Binary Function that copies the properties of an edge in the original graph into the corresponding edge in the copy.
> Default: `edge_copier<VertexListGraph, MutableGraph>` which uses the property tag `edge_all` to access a property map from the graph.

IN: `vertex_index_map(VertexIndexMap i_map)`

> The vertex index map type must be a model of Readable Property Map and must map the vertex descriptors of `G` to the integers from 0 to `num_vertices(G)`.
> Default: `get(vertex_index, G)` Note: if you use this default, make sure your graph has an internal `vertex_index` property. For example, `adjacenty_list` with `VertexList=listS` does not have an internal `vertex_index` property.

UTIL/OUT: `orig_to_copy(Orig2CopyMap c)`

> This maps vertices in the original graph to vertices in the copy. Default: an iterator_property_map created from a `std::vector` of the output graph's vertex descriptor type of size `num_vertices(g)` and using the `i_map` for the index map.

### Complexity

The time complexity is O(V + E).

Copyright © 2000-2001 | Jeremy Siek, Indiana University (jsiek@osl.iu.edu)