三人三鬼过河 Java实现

 题目是这样的:

3人3鬼在一条河岸的一边，都要到河的另一边去，河边停靠有一条船，最多可以载一人一鬼，或2鬼，或2人，不论何时不管河岸的那一边只要鬼的数量超过人的数量，鬼都会吃掉人导致过河失败：用java 找出过河的方法

实现代码如下:

import java.util.ArrayList; import java.util.List; enum Track { ONE_HUMAN, TWO_HUMAN, ONE_HUMAN_ONE_GHOST, ONE_GHOST, TWO_GHOST, ERROR; @Override public String toString() { return this.name(); } public Track next() { if (this.equals(ONE_HUMAN)) { return TWO_HUMAN; } if (this.equals(TWO_HUMAN)) { return ONE_HUMAN_ONE_GHOST; } if (this.equals(ONE_HUMAN_ONE_GHOST)) { return ONE_GHOST; } if (this.equals(ONE_GHOST)) { return TWO_GHOST; } if (this.equals(TWO_GHOST)) { return ERROR; } return ERROR; } } enum Direction { GO, BACK; @Override public String toString() { return this.name(); } } class History { Track t = Track.ONE_HUMAN; Direction d = Direction.BACK; public static int COUNT = 3; int srcHuman = COUNT; int srcGhost = COUNT; int aimHuman = 0; int aimGhost = 0; public static List<History> history = new ArrayList<History>(); public static List<History> error_history = new ArrayList<History>(); public static void init(int c) { COUNT = c; history.clear(); history.add(new History()); } public History() { } public History(int sh, int sg, int ah, int ag) { this.srcHuman = sh; this.srcGhost = sg; this.aimHuman = ah; this.aimGhost = ag; } public History(int sh, int sg, int ah, int ag, Direction d, Track t) { this.srcHuman = sh; this.srcGhost = sg; this.aimHuman = ah; this.aimGhost = ag; this.d = d; this.t = t; } public History(int sh, int sg, int ah, int ag, Direction d) { this.srcHuman = sh; this.srcGhost = sg; this.aimHuman = ah; this.aimGhost = ag; this.d = d; } @Override public String toString() { return t + (t.toString().length() > 10 ? "/t" : t.toString().length() < 9 ? "/t/t/t" : "/t/t") + d + "/t/t" + srcHuman + "/t/t" + srcGhost + "/t/t" + aimHuman + "/t/t" + aimGhost; } private void printHistory() { System.out.println("Track" + "/t/t/t" + "Direct" + "/t/t" + "srcHuman" + "/t" + "srcGhost" + "/t" + "aimHuman" + "/t" + "aimGhost"); int i = 0; for (History h : history) { if (i != 0) System.out.println(h); i++; } // System.out.println("********************"); // // for (History h : error_history) { // if (!(h.srcGhost == 3 && h.srcHuman == 3)) // System.out.println(h); // } } @Override public boolean equals(Object o) { if (o instanceof History && o != null) { History h = (History) o; return h.srcHuman == srcHuman && h.srcGhost == srcGhost && h.aimGhost == aimGhost && h.aimHuman == aimHuman && h.d.equals(d); } return false; } private boolean checkRecercle(History h) { return history.contains(h); } public void go(Track begin, Direction dir) { if (srcHuman == 0 && srcGhost == 0) { printHistory(); return; } d = dir; Direction back = dir.equals(Direction.GO) ? Direction.BACK : Direction.GO; if (begin.equals(Track.ONE_HUMAN)) { if (oneHuman(dir)) { History h = new History(srcHuman, srcGhost, aimHuman, aimGhost, dir, begin); history.add(h); error_history.add(h); go(Track.ONE_HUMAN, back); return; } begin = Track.TWO_HUMAN; } if (begin.equals(Track.TWO_HUMAN)) { if (twoHuman(dir)) { History h = new History(srcHuman, srcGhost, aimHuman, aimGhost, dir, begin); history.add(h); error_history.add(h); go(Track.ONE_HUMAN, back); return; } begin = Track.ONE_HUMAN_ONE_GHOST; } if (begin.equals(Track.ONE_HUMAN_ONE_GHOST)) { if (oneHumanOneGhost(dir)) { History h = new History(srcHuman, srcGhost, aimHuman, aimGhost, dir, begin); history.add(h); error_history.add(h); go(Track.ONE_HUMAN, back); return; } begin = Track.ONE_GHOST; } if (begin.equals(Track.ONE_GHOST)) { if (oneGhost(dir)) { History h = new History(srcHuman, srcGhost, aimHuman, aimGhost, dir, begin); history.add(h); error_history.add(h); go(Track.ONE_HUMAN, back); return; } begin = Track.TWO_GHOST; } if (begin.equals(Track.TWO_GHOST)) { if (twoGhost(dir)) { History h = new History(srcHuman, srcGhost, aimHuman, aimGhost, dir, begin); history.add(h); error_history.add(h); go(Track.ONE_HUMAN, back); return; } begin = Track.ERROR; } if (begin.equals(Track.ERROR)) { revert(); } } private void renew(History h) { this.d = h.d; this.t = h.t; this.srcGhost = h.srcGhost; this.aimGhost = h.aimGhost; this.srcHuman = h.srcHuman; this.aimHuman = h.aimHuman; } private void revert() { // error_history.add(history.get(history.size() - 1)); Track tb = history.get(history.size() - 1).t.next(); Direction db = history.get(history.size() - 1).d; error_history.add(new History(history.get(history.size() - 1).srcHuman, history.get(history.size() - 1).srcGhost, history.get(history .size() - 1).aimHuman, history.get(history.size() - 1).aimGhost, history.get(history .size() - 1).d, Track.ERROR)); if (history.size() == 1) { System.out.println("Failed, "); return; } history.remove(history.size() - 1); renew(history.get(history.size() - 1)); go(tb, db); } private boolean twoGhost(Direction d) { switch (d) { case GO: if (srcGhost < 2) { return false; } else { if (aimGhost + 2 > aimHuman && aimHuman > 0) { return false; } else { if (checkRecercle(new History(srcHuman, srcGhost - 2, aimHuman, aimGhost + 2, d))) { return false; } srcGhost = srcGhost - 2; aimGhost = aimGhost + 2; return true; } } case BACK: if (aimGhost < 2) { return false; } else { if (srcGhost + 2 > srcHuman && srcHuman > 0) { return false; } else { if (checkRecercle(new History(srcHuman, srcGhost + 2, aimHuman, aimGhost - 2, d))) { return false; } srcGhost = srcGhost + 2; aimGhost = aimGhost - 2; return true; } } } return false; } private boolean oneGhost(Direction d) { switch (d) { case GO: if (srcGhost < 1) { return false; } else { if (aimGhost + 1 > aimHuman && aimHuman > 0) { return false; } else { if (checkRecercle(new History(srcHuman, srcGhost - 1, aimHuman, aimGhost + 1, d))) { return false; } srcGhost--; aimGhost++; return true; } } case BACK: if (aimGhost < 1) { return false; } else { if (srcGhost + 1 > srcHuman && srcHuman > 0) { return false; } else { if (checkRecercle(new History(srcHuman, srcGhost + 1, aimHuman, aimGhost - 1, d))) { return false; } srcGhost++; aimGhost--; return true; } } } return false; } private boolean oneHumanOneGhost(Direction d) { switch (d) { case GO: if (srcHuman < 1 || srcGhost < 1) { return false; } else { if (aimHuman < aimGhost) { return false; } if (checkRecercle(new History(srcHuman - 1, srcGhost - 1, aimHuman + 1, aimGhost + 1, d))) { return false; } srcHuman--; srcGhost--; aimHuman++; aimGhost++; return true; } case BACK: if (aimHuman < 1 || aimGhost < 1) { return false; } else { if (checkRecercle(new History(srcHuman + 1, srcGhost + 1, aimHuman - 1, aimGhost - 1, d))) { return false; } if (srcHuman < srcGhost) { return false; } aimHuman--; aimGhost--; srcHuman++; srcGhost++; return true; } } return false; } private boolean twoHuman(Direction d) { switch (d) { case GO: if (srcHuman < 2) { return false; } else { if (srcHuman - 2 < srcGhost && srcHuman - 2 > 0 || (aimHuman + 2 < aimGhost)) { return false; } else { if (checkRecercle(new History(srcHuman - 2, srcGhost, aimHuman + 2, aimGhost, d))) { return false; } srcHuman = srcHuman - 2; aimHuman = aimHuman + 2; return true; } } case BACK: if (aimHuman < 2) { return false; } else { if (aimHuman - 2 < aimGhost && aimHuman - 2 > 0 || (srcHuman + 2 < srcGhost)) { return false; } else { if (checkRecercle(new History(srcHuman + 2, srcGhost, aimHuman - 2, aimGhost, d))) { return false; } srcHuman = srcHuman + 2; aimHuman = aimHuman - 2; return true; } } } return false; } private boolean oneHuman(Direction d) { switch (d) { case GO: if (srcHuman < 1) { return false; } else { if (srcHuman - 1 < srcGhost && srcHuman - 1 > 0 || (aimHuman + 1 < aimGhost)) { return false; } else { if (checkRecercle(new History(srcHuman - 1, srcGhost, aimHuman + 1, aimGhost, d))) { return false; } srcHuman--; aimHuman++; return true; } } case BACK: if (aimHuman < 1) { return false; } else { if (aimHuman - 1 < aimGhost && aimHuman - 1 > 0 || (srcHuman + 1 < srcGhost)) { return false; } else { if (checkRecercle(new History(srcHuman + 1, srcGhost, aimHuman - 1, aimGhost, d))) { return false; } srcHuman++; aimHuman--; return true; } } } return false; } } public class Demo { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub History.init(6); History h = new History(); h.go(Track.ONE_HUMAN, Direction.GO); } }