graph-basic

打算使用STL中的vector，通过邻接链表的方式存储图。这里贴基本定义，以及depth-first-search和breadth-first-search的实现代码。

其他图的算法实现，就贴在各自的算法解释之后吧。喵。

#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;  

// define vertex in graph
typedef struct Vertex {
    int id;
    vector<int> neighbors;
    Vertex() {
    	id = -1;
	}
    Vertex(int nid){
    	id = nid;
	}
} Vertex;
// define graph
typedef struct Graph {
    // Vertex of Graph
    vector<Vertex> vertexes;
    // number of vertexes
    int nVertexes;
    bool isDAG;

	// construct function
    Graph(int n, bool isDAG) : nVertexes(n), isDAG(isDAG) { vertexes.resize(n); }  

    // add edge.
    bool addEdge(int id1, int id2) {
        if (max(id1, id2) >= vertexes.size())
		    return false;
        if (isDAG) {
            vertexes[id1].neighbors.push_back(id2);
        }
        else {
            vertexes[id1].neighbors.push_back(id2);
            vertexes[id2].neighbors.push_back(id1);
        }
        return true;
    }  

    // depth first search
    vector<int> DFS(int start) {
        set<int> visited;
        vector<int> g, result;
        g.push_back(start);
        visited.insert(start);
        result.push_back(start);
        bool found;
        while(g.size() > 0) {
            int id = g[g.size()-1];
            found = false;
            for(int i = 0; i < vertexes[id].neighbors.size(); i++) {
                int id1 = vertexes[id].neighbors[i];
                if (visited.count(id1) == 0) {
                    g.push_back(id1);
                    result.push_back(id1);
                    visited.insert(id1);
                    found = true;
                    break;
                }
            }
            // all neighbors have been visited
            if (!found) {
                int id2 = g[g.size()-1];
                //result.push_back(-1 * id2);
                //cout << "pop " << id2 << " ";
                g.pop_back();
            }
        }
        return result;
    }

    // breadth first search
    vector<int> BFS(int start) {
		set<int> visited;
        vector<int> g, result;
		// temporary store
        g.push_back(start);
        visited.insert(start);
        while(g.size() > 0) {
            int id = g[0];
            g.erase(g.begin());
            result.push_back(id);
            for(int i = 0; i < vertexes[id].neighbors.size(); i++) {
                int id1 = vertexes[id].neighbors[i];
                // if id1 is unvisited
                if (visited.count(id1) == 0) {
                    g.push_back(id1);
                    visited.insert(id1);
                }
            }
        }
        return result;
    }
} Graph;  

int main() {
    Graph g(8, true);
    g.addEdge(0, 1);
    g.addEdge(0, 3);
    g.addEdge(1, 2);
    g.addEdge(3, 4);
    g.addEdge(3, 5);
    //g.addEdge(4, 5);
    //g.addEdge(4, 6);
    g.addEdge(5, 6);
    g.addEdge(5, 7);
    //g.addEdge(6, 7);
    vector<int> bv = g.BFS(0);
    cout << "宽度优先搜索节点顺序：";
    for(int j = 0; j < bv.size(); j++)
        cout << bv[j] << " ";
    cout << endl;  

    bv = g.DFS(0);
    for(int j = 0; j < bv.size(); j++)
        cout << bv[j] << " ";
    cout << endl; 

    cout << "深度优先搜索节点顺序：";
    Graph g1(6, false);
    g1.addEdge(0, 1);
    g1.addEdge(0, 4);
    g1.addEdge(0, 5);
    g1.addEdge(1, 5);
    g1.addEdge(4, 5);
    g1.addEdge(5, 2);
    g1.addEdge(5, 3);
    g1.addEdge(2, 3);
    vector<int> route = g1.DFS(0);
    for(int i = 0; i < route.size(); i++)
        cout << route[i] << " ";
    cout << endl;  

    return 0;
}