java 实现N个女人过桥问题

来源：互联网发布：淘宝客服处理问题案例编辑：程序博客网时间：2024/05/01 02:43

题目描述：

N个女人过桥，夜间有一火把，每次最多过两个，必需带火把，过桥速度不一样。过去后必须回来一个人，把火把带回来。要求女人都过去，实现最小过桥时间。

如果4个女人过桥，时间为1,2,5,10，那么最小时间是17。

思路：

在未过桥中选最少时间的两个人过桥，当过桥后选最少时间的人返回，此时火把交给返回的人，同时对己过桥的人进行统计，当还有三人未过桥时（包含返的人），

让时间最大的两个人过桥，后将为把交给过桥后最少时间的再返回，最后两个最少时间的人过桥。

比如1,2,5,9,10, 那么1,2 先过1回来,1,5过,1回来,剩3个的时候, 9,10过,2回来, 1,2过,OK

代码实现：

package NWomenCrossBridge;import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.LinkedList;import java.util.List;import java.util.Queue;import java.util.Stack;import org.apache.log4j.Logger;public class NWomenCrossBridge {private Logger logger = Logger.getLogger(NWomenCrossBridge.class);private static NWomenCrossBridge instance = null;private static Stack<Integer> UnCross = null;private static Queue<Integer> Crossed = null;private static int timeCost = 0;public static NWomenCrossBridge getInstance(Integer... needTime) {if(instance == null) {return new NWomenCrossBridge(needTime);}return instance;}private NWomenCrossBridge(Integer... needTime) {UnCross = new Stack<Integer>();Crossed = new LinkedList<Integer>();//队列setTime(needTime);}public void setTime(Integer... needTime) {List<Integer> list = new ArrayList<Integer>();list = Arrays.asList(needTime);Collections.sort(list);for(int i=list.size()-1;i>=0;i--) UnCross.push(list.get(i));}public void crossBridge() {Integer first = null;Integer second = null;Integer third = null;int count = 1;while(UnCross.size()>0) {if(UnCross.size()>3) {first = UnCross.pop();second = UnCross.pop();Crossed.offer(second);timeCost += second;//过桥时间UnCross.push(first);timeCost += first; //回程时间logger.info("第" + count + "次,"+ first +" 和  " + second + " 同过桥, " + first + " 返回");count++;} else if(UnCross.size() == 3){first = UnCross.pop();second = UnCross.pop();third = UnCross.pop();Crossed.offer(second);Crossed.offer(third);timeCost += third;//过桥时间Integer goBack = Crossed.poll();//已过桥的，把其中最小的拿出来返回timeCost += goBack;//回程时间logger.info("第" + count + "次,"+ second +" 和  " + third + " 同过桥, " + goBack + " 返回");count++;Crossed.offer(first);Crossed.offer(goBack);timeCost += goBack;logger.info("第" + count + "次,"+ first +" 和  " + goBack + " 同过桥");}}logger.info("总过桥次数为: " + count + " 总过桥时间为: " + timeCost);}public static void main(String[] args) {NWomenCrossBridge nWomenCrossBridge = NWomenCrossBridge.getInstance(1,2,5,9,10);  //时间指定，可以无序nWomenCrossBridge.crossBridge();}}

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