Hamilton

package com.test;import java.util.Vector;public class Hamilton {protected int start;protected int a[][];protected int len;protected int x[]; // 记录回路protected boolean flag;public Hamilton(int[][] a, int n, int start) {this.a = a;this.len = n;this.flag = false;this.x = new int[n];this.start = start - 1;}public boolean isComplete(int k) {return a[x[k - 1]][x[0]] == 1;}public Vector<Integer> makeIterms(int k) {Vector<Integer> iterms = new Vector<Integer>();if (k == 0) {iterms.add(start);} else {for (int i = 0; i < len; i++)if (a[x[k - 1]][i] == 1) // 相当重要iterms.add(i);}return iterms; // 第k-1层结点的所有临界点}public void printSolution(int k) {System.out.print(x[0] + 1);for (int i = 1; i < len; i++)System.out.print("->" + (x[i] + 1));System.out.println("->" + (x[0] + 1));}public boolean isPartial(int k) {for (int i = 0; i < k; i++)if (x[i] == x[k])return false;return true;}}public class General {// 回溯算法的引导框架public static void backtrack(Hamilton p) {explore(p, 0);if (!p.flag)System.out.println("no sulution!");}// 回溯算法的探索框架private static void explore(Hamilton p, int k) {if (k >= p.len) {if (p.isComplete(k)) {p.flag = true;p.printSolution(k);}return;}Vector<Integer> iterms = p.makeIterms(k);for (int i = 0; i < iterms.size(); i++) {p.x[k] = iterms.get(i);if (p.isPartial(k))explore(p, k + 1);}}public static void main(String args[]) {int c[][] = { { 0, 1, 1, 1, 0 }, { 1, 0, 1, 0, 1 }, { 1, 1, 0, 1, 0 },{ 1, 0, 1, 0, 1 }, { 0, 1, 0, 1, 0 } };Hamilton p;p = new Hamilton(c, 5, 1);General.backtrack(p);}}