leetcode/src/main/java/basic/search/BreadthFirstSearch.java at master · onelogistics/leetcode · GitHub

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packagebasic.search;

importjava.util.ArrayList;
importjava.util.List;
importjava.util.Queue;
importjava.util.concurrent.LinkedBlockingDeque;

publicclassBreadthFirstSearch {
privateintM;
privateintN;
privateintDOWN=1;
privateintRIGHT=2;
privateSearchIteambestIteam;
privateList<SearchIteam> queue=newArrayList<SearchIteam>();
classSearchIteam {
privateintcurX;
privateintcurY;
privateintdir;
privateintvalue;
privateSearchIteamlastIteam;

publicSearchIteam(intcurX, intcurY, intdir, intvalue) {
this.curX = curX;
this.curY = curY;
this.dir = dir;
this.value = value;
 }
 }

/**
 * 如果找到且队列中的value较小，替换
 * @param newIteam
 * @return 是否在搜索队列中找到相应Iteam
 */
privatebooleanreplaceIteam(SearchIteamnewIteam) {
booleanfind=false;
for (inti=0;i<queue.size();i++) {
SearchIteamsearchIteam=queue.get(i);
if(searchIteam.curX==newIteam.curX && searchIteam.curY == newIteam.curY) {
find=true;
if(searchIteam.value<newIteam.value) {
queue.remove(i);
queue.add(newIteam);
 }
break;
 }
 }
returnfind;
 }

/**
 * 观察了下，似乎重复的元素都是位于搜索队列最后一个元素，是否可以只比对最后一个元素
 * @param newIteam
 * @return
 */
privatebooleanreplaceIteam2(SearchIteamnewIteam) {
booleanfind=false;
if(queue.size()!=0) {
SearchIteamsearchIteam=queue.get(queue.size()-1);
if(searchIteam.curX==newIteam.curX && searchIteam.curY == newIteam.curY) {
find=true;
if(searchIteam.value<newIteam.value) {
queue.remove(queue.size()-1);
queue.add(newIteam);
 }
 }
 }
returnfind;
 }
privatevoidsearch(int[][] matrix) {
while (queue.size()>0) {
SearchIteamsearchIteam=queue.remove(0);
intcurX=searchIteam.curX;
intcurY=searchIteam.curY;
intcurValue=searchIteam.value;
if(curX==M-1 && curY==N-1) {
bestIteam=searchIteam;
 }
if(curX<M-1) {
SearchIteamnewItem=newSearchIteam(curX+1,curY,DOWN,curValue+matrix[curX+1][curY]);
newItem.lastIteam=searchIteam;
if(!replaceIteam2(newItem)) {
queue.add(newItem);
 }
 }
if(curY<N-1) {
SearchIteamnewItem=newSearchIteam(curX,curY+1,RIGHT,curValue+matrix[curX][curY+1]);
newItem.lastIteam=searchIteam;
if(!replaceIteam2(newItem)) {
queue.add(newItem);
 }
 }
 }
 }
publicintgetMaxAward(int[][] matrix) {
M=matrix.length;
N=matrix[0].length;
SearchIteamsearchIteam=newSearchIteam(0,0,0,matrix[0][0]);
queue.add(searchIteam);
search(matrix);
returnbestIteam.value;
 }
publicvoidprintBestPath() {
List<Integer> dirList=newArrayList<>();
SearchIteamcurIteam=bestIteam;
while (curIteam!=null) {
dirList.add(curIteam.dir);
curIteam=curIteam.lastIteam;
 }
//从dirList.size()-2开始输出，不输出起始点的dir
for (inti=dirList.size()-2;i>=0;i--) {
if(dirList.get(i) == DOWN) {
System.out.print("下 ");
 } elseif(dirList.get(i) == RIGHT) {
System.out.print("右 ");
 }
 }
System.out.println();
 }
}