hamilton

Author: iScript

.idea/workspace.xml

@@ -0,0 +1,6 @@
+4 5
+0 1
+0 2
+0 3
+1 2
+1 3

g4.txt

@@ -0,0 +1,70 @@
+import java.util.ArrayList;
+import java.util.Collections;
+
+public class HamiltonLoop {
+    private Graph G;
+    private boolean[] visited;
+    private int[] pre;
+    private int end;
+
+    public HamiltonLoop(Graph G){
+        this.G = G;
+        visited = new boolean[G.V()];
+        pre = new int[G.V()];
+        end = -1;
+
+        dfs(0,0);
+    }
+
+    // 深度优先遍历
+    private boolean dfs(int v,int parent){
+        visited[v] = true;
+        pre[v] = parent;
+
+        // 遍历相邻节点
+        for(int w : G.adj(v)){
+            if(!visited[w]){
+                if(dfs(w,v)) return true;
+            }
+            else if(w == 0 && allVisited()){    // 如果回到起始点0并且所有的点都被访问过了，则找到了哈密尔回路
+                end = v;
+                return true;
+            }
+
+        }
+
+        // 回溯
+        visited[v] = false;
+        return false;
+
+
+    }
+
+    private boolean allVisited(){
+        for(int v = 0;v<G.V();v++){
+            if(!visited[v]) return false;
+        }
+        return true;
+    }
+
+    private ArrayList<Integer> result(){
+        ArrayList<Integer> res = new ArrayList<>();
+        if(end == -1) return res;
+
+        int cur = end;
+        while(cur != 0){
+            res.add(cur);
+            cur = pre[cur]; // 上一个节点
+        }
+        res.add(0);
+        Collections.reverse(res);   // 反
+        return res;
+    }
+
+    public static void main(String[] args){
+
+        Graph g = new Graph("g4.txt");
+        HamiltonLoop hamiltonLoop = new HamiltonLoop(g);
+        System.out.println(hamiltonLoop.result());
+    }
+}