leetcode Ch7-Graph Search

 1. Clone Graph

BFS:

class Solution {
public:
    typedef UndirectedGraphNode UGNode;
    UndirectedGraphNode* cloneGraph(UndirectedGraphNode* node) {
        if (node == NULL) {
            return NULL;
        }
        vector<UGNode*> nodes;
        unordered_map<UGNode*, UGNode*> umap;
        
        //clone nodes only
        nodes.push_back(node);
        umap[node] = new UGNode(node->label);
        int start = 0;
        while (start < nodes.size()) {
            UGNode* tmp = nodes[start];
            start++;
            for (int i = 0; i < tmp->neighbors.size(); i++) {
                if (umap.count(tmp->neighbors[i]) == 0) {
                    nodes.push_back(tmp->neighbors[i]);
                    umap[tmp->neighbors[i]] = new UGNode(tmp->neighbors[i]->label);
                }
            }
        }
        
        //clone neighbors only
        for (int i = 0; i < nodes.size(); i++) {
            UGNode* newNode = umap[nodes[i]];
            for (int j = 0; j < nodes[i]->neighbors.size(); j++) {
                newNode->neighbors.push_back(umap[nodes[i]->neighbors[j]]);    
            }
        }
        return umap[node];
    }
};

DFS:

class Solution {
public:
    typedef UndirectedGraphNode UGNode;
    UndirectedGraphNode* cloneGraph(UndirectedGraphNode* node) {
        if (node == NULL) {
            return NULL;
        }
        return dfs(node);
    }
    
    UGNode* dfs(UGNode* node) {
        UGNode* p = new UGNode(node->label);
        umap[p->label] = p;
        for (int i = 0; i < node->neighbors.size(); i++) {
            if (umap.count(node->neighbors[i]->label) == 0) {
                p->neighbors.push_back(dfs(node->neighbors[i]));
            } else {
                p->neighbors.push_back(umap[node->neighbors[i]->label]);
            }
        }
        return p;
    }
private:
    unordered_map<int, UGNode*> umap;
};

这里umap里的second存的都是copy后的图节点，不是原图。

图的邻接表DFS：

struct VertexNode {
    int data;
    EdgeNode* next;
};

struct EdgeNode {
    int index; // 存储其对应的点的下标
    EdgeNode* next;
};

struct Graph {
    VertexNode vexs[MAXVEX];
    int numVertex;
};

vector<bool> visited;

void dfs(Graph* g, int i) {
    visited[i] = 1;
    print(g, i);
    EdgeNode* p = g->vexs[i]->next;
    while (p) {
        if (!visited[p->index]) {
            dfs(g, p->index);
        }
        p = p->next;
    }
}

void dfsTraverse(Graph* g) {
    for (int i = 0; i < g->numVertex; i++) {
        if (!visited[i]) {
            dfs(g, i);
        }
    }
}

图的邻接表BFS：

void bfsTraverse(Graph* g) {
    queue<int> q;
    for (int i = 0; i < numVertex; i++) {
        if (!visited[i]) {
            visited[i] = 1;
            print(g, i);
            q.push(i);
            while (!q.empty()) {    
                int j = q.top();
                q.pop();
                EdgeNode* p = g->vexs[j].next;
                while (p) {
                    if (!visited[p->index]) {
                        visited[p->index] = 1;
                        print(g, p->index);
                        q.push(p->index);
                    }
                    p = p->next;
                }
            }
        }
    }
}