DFS深度优先搜索算法与BFS广度优先搜索算法的java实现

广度优先搜索算法

package graph;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;import java.util.Stack;public class BFS {public class Node{/** * 节点的标识符 */private Integer identifier;/** * 该节点是否被访问过 */private boolean visited = false;/** * 该节点与其他节点的映射关系 */private Map<Node,Integer> mapping = new HashMap<Node,Integer>();public Integer getIdentifier() {return identifier;}public void setIdentifier(Integer identifier) {this.identifier = identifier;}public boolean isVisited() {return visited;}public void setVisited(boolean visited) {this.visited = visited;}public Map<Node, Integer> getMapping() {return mapping;}}public static Stack<Node> searchByBFS(Node src, Node target) {// TODO Auto-generated method stubreturn bfs(src, target, false, new Stack<Node>());}/** * 广度优先搜索 * 遍历起点的所有相邻节点，若无目标节点，选择一个节点为起点继续递归搜索 * 若已无未被访问过的相邻节点，则结束本次递归，该节点出栈 * @param src 起点 * @param target 目标节点 * @param isFound 是否已搜索到 * @param path 记录路径 * @return 路径栈 */public static Stack<Node> bfs(Node src, Node target, boolean isFound, Stack<Node> path) {if(!isFound) {path.add(src);Map<Node, Integer> mapping = src.getMapping();Iterator<Entry<Node, Integer>> entryIterator = mapping.entrySet().iterator();while (entryIterator.hasNext()) {Map.Entry<Node, Integer> entry = (Map.Entry<Node, Integer>) entryIterator.next();Node nextNode = entry.getKey();if (nextNode.getIdentifier() == target.getIdentifier()) {isFound = true;path.add(nextNode);return path;}}//在src的相邻节点中未找到target，则选择一个相邻节点作为src开始递归entryIterator = mapping.entrySet().iterator();while (entryIterator.hasNext()) {Map.Entry<Node, Integer> entry = (Map.Entry<Node, Integer>) entryIterator.next();Node nextNode = entry.getKey();if(!path.contains(nextNode) && nextNode.getMapping().size() != 0) {Stack<Node> temp = bfs(nextNode, target, isFound, path);if(temp == null) {continue;}return temp;}}if(!isFound) {path.remove(src);return null;}}return path;}}

测试：

package graph.test;import graph.BFS;import graph.BFS.Node;import graph.DFS;import java.util.Iterator;import java.util.Stack;public class BFSTest {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubBFS bfs = new BFS();BFS.Node node_1 = bfs.new Node();BFS.Node node_2 = bfs.new Node();BFS.Node node_3 = bfs.new Node();BFS.Node node_4 = bfs.new Node();BFS.Node node_5 = bfs.new Node();BFS.Node node_6 = bfs.new Node();node_1.setIdentifier(1);node_1.getMapping().put(node_2, 7);node_1.getMapping().put(node_3, 9);node_1.getMapping().put(node_6, 14);node_2.setIdentifier(2);node_2.getMapping().put(node_1, 7);node_2.getMapping().put(node_3, 10);node_2.getMapping().put(node_4, 15);node_3.setIdentifier(3);node_3.getMapping().put(node_1,7);node_3.getMapping().put(node_2,10);node_3.getMapping().put(node_4,11);node_3.getMapping().put(node_6,2);node_4.setIdentifier(4);node_4.getMapping().put(node_3, 11);node_4.getMapping().put(node_2, 15);node_4.getMapping().put(node_5, 6);node_5.setIdentifier(5);node_5.getMapping().put(node_4, 6);node_5.getMapping().put(node_6, 9);node_6.setIdentifier(6);node_6.getMapping().put(node_5, 9);node_6.getMapping().put(node_1, 14);Stack<Node> path = BFS.searchByBFS(node_2, node_6);System.out.println("-------The BFS path--------");for (Iterator<Node> iterator = path.iterator(); iterator.hasNext();) {Node node = (Node) iterator.next();if (iterator.hasNext()) {System.out.print(node.getIdentifier()+"-->");}else{System.out.print(node.getIdentifier());}}}}

结果：

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深度有限

package graph;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;import java.util.Stack;/** * Depth first search * @author Administrator * */public class DFS {public class Node{/** * 节点的标识符 */private Integer identifier;/** * 该节点是否被访问过 */private boolean visited = false;/** * 该节点与其他节点的映射关系 */private Map<Node,Integer> mapping = new HashMap<Node,Integer>();public Integer getIdentifier() {return identifier;}public void setIdentifier(Integer identifier) {this.identifier = identifier;}public boolean isVisited() {return visited;}public void setVisited(boolean visited) {this.visited = visited;}public Map<Node, Integer> getMapping() {return mapping;}}public static Stack<Node> searchByDFS(Node src, Node target) {return dfs(src, target, false, new Stack<Node>());}/** * 深度优先搜索算法 * 从起始节点开始，判断相邻的第一个未被访问的节点，若不是目标节点， * 且该节点还有未被访问的节点，则该节点入栈并递归。 * 局部递归结束条件： * 1、若没有下一个未被访问的相邻节点，则该节点出栈 * 2、搜索到目标节点，该节点入栈，结束递归 * @param src 起始节点 * @param target 目标节点 * @param path 路径栈 * @return 路径栈 */public static Stack<Node> dfs(Node src, Node target, boolean isFound, Stack<Node> path){//未找到目标节点，起始时判断可提高性能if(!isFound){//当前节点入栈path.add(src);//遍历相邻节点Map<Node, Integer> mapping = src.getMapping();Iterator<Entry<Node, Integer>> entryIterator = mapping.entrySet().iterator();while (entryIterator.hasNext()) {//未找到目标节点Entry<Node, Integer> entry = (Entry<Node, Integer>) entryIterator.next();Node nextNode = entry.getKey();//判断下一节点是否在路径中if(!path.contains(nextNode)){//判断是否为目标节点if(nextNode.getIdentifier() == target.getIdentifier()) {isFound = true;path.add(nextNode);break;}//不是目标节点，且下一节点仍有相邻节点，则以nextNode作为下一递归的srcif(nextNode.getMapping().size() != 0) {Stack<Node> temp = dfs(nextNode, target, isFound, path);if(temp == null) continue;return temp;}}}//没有下一个未被访问的相邻节点且未找到目标节点，当前节点出栈，回溯if(!isFound) {path.remove(src);return null;}}return path;}}

测试：

package graph.test;import graph.DFS;import graph.DFS.Node;import java.util.Iterator;import java.util.Stack;public class DFSTest {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubDFS dfs = new DFS();DFS.Node node_1 = dfs.new Node();DFS.Node node_2 = dfs.new Node();DFS.Node node_3 = dfs.new Node();DFS.Node node_4 = dfs.new Node();DFS.Node node_5 = dfs.new Node();DFS.Node node_6 = dfs.new Node();node_1.setIdentifier(1);node_1.getMapping().put(node_2, 7);node_1.getMapping().put(node_3, 9);node_1.getMapping().put(node_6, 14);node_2.setIdentifier(2);node_2.getMapping().put(node_1, 7);node_2.getMapping().put(node_3, 10);node_2.getMapping().put(node_4, 15);node_3.setIdentifier(3);node_3.getMapping().put(node_1,7);node_3.getMapping().put(node_2,10);node_3.getMapping().put(node_4,11);node_3.getMapping().put(node_6,2);node_4.setIdentifier(4);node_4.getMapping().put(node_3, 11);node_4.getMapping().put(node_2, 15);node_4.getMapping().put(node_5, 6);node_5.setIdentifier(5);node_5.getMapping().put(node_4, 6);node_5.getMapping().put(node_6, 9);node_6.setIdentifier(6);node_6.getMapping().put(node_5, 9);node_6.getMapping().put(node_1, 14);Stack<Node> path = DFS.searchByDFS(node_1, node_6);System.out.println("-------The DFS path--------");for (Iterator<Node> iterator = path.iterator(); iterator.hasNext();) {Node node = (Node) iterator.next();if (iterator.hasNext()) {System.out.print(node.getIdentifier()+"-->");}else{System.out.print(node.getIdentifier());}}}}

结果：