华为笔试9.9 AC3 Java
1. 完美排列 第一题靠运气过的，我反复提交了将近一个小时，出了一次AC，别的一直各种10%，20%，30%，50%，60%，90%…
#笔经##华为#
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int [][] prefect = new int [n][2];
for(int i =0;i<n*2;i++) {
if (i < n ) {
prefect[i][0] = sc.nextInt();
} else {
prefect[i-n][1] = sc.nextInt();
}
}
int m = sc.nextInt();
int [][] temp = new int [m][2];
Queue<Integer> queue = new LinkedList<>();
for(int i =0;i<m*2;i++){
if(i < m){
temp[i][0] = sc.nextInt();
}else{
temp[i-m][1] = sc.nextInt();
}
}
for(int i=0;i<m-prefect.length;i++){
if(temp[i][0] == prefect[0][0]&&temp[i][1] == prefect[0][1]){
queue.add(i);
}
}
int result = 0;
while(!queue.isEmpty()){
int position = queue.poll();
result = position+1;
boolean flag = false;
int index = 0;
for(int i = position;i<m;i++){
if(index==prefect.length){
flag = true;
break;
}
else if(temp[i][0] == prefect[index][0]&&temp[i][1] == prefect[index][1]){
index++;
}else{
result = 0;
break;
}
}
if(flag){
break;
}
}
System.out.println(result);
}
} 2.最长水沟
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int m = sc.nextInt();
int [][] map = new int [n][m];
for(int i = 0;i<n;i++){
for(int j =0;j<m;j++){
map[i][j] = sc.nextInt();
}
}
int result = 0;
for(int i = 0;i<n;i++){
for(int j =0;j<m;j++){
int temp = track(map,i,j,Integer.MAX_VALUE,0);
if(temp>result){
result = temp;
}
}
}
System.out.println(result);
}
public static int track(int [][] map,int x,int y,int ori,int result){
if(x<0||x>=map.length||y<0||y>=map[0].length){
return result;
}
if(map[x][y]>=ori){
return result;
}
result++;
return Math.max(Math.max(track(map,x-1,y,map[x][y],result),track(map,x+1,y,map[x][y],result)),Math.max(track(map,x,y-1,map[x][y],result),track(map,x,y+1,map[x][y],result)));
}
} 3.树最大异或路径import java.util.HashMap;
import java.util.Scanner;
public class Main {
static int result = 0;
public static class TreeNode{
int id;
int value;
int left_id;
int right_id;
TreeNode left;
TreeNode right;
public TreeNode() {
}
public TreeNode(int id, int value) {
this.id = id;
this.value = value;
}
public TreeNode(int id, int value, int left_id, int right_id) {
this.id = id;
this.value = value;
this.left_id = left_id;
this.right_id = right_id;
}
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
HashMap<Integer,TreeNode> map = new HashMap<>();
for(int i =0;i<n;i++){
int node_id = sc.nextInt();
int node_value = sc.nextInt();
int left_id = sc.nextInt();
int right_id = sc.nextInt();
TreeNode treeNode = new TreeNode(node_id,node_value,left_id,right_id);
map.put(node_id,treeNode);
}
for(Integer key:map.keySet()){
TreeNode treeNode = map.get(key);
if(treeNode.left_id!=-1){
treeNode.left = map.get(treeNode.left_id);
}
if(treeNode.right_id!=-1){
treeNode.right = map.get(treeNode.right_id);
}
}
for(Integer key:map.keySet()){
TreeNode treeNode = map.get(key);
dfs(treeNode,0);
}
System.out.println(result);
}
public static void dfs(TreeNode node,int value){
if(node==null){
return;
}
value = value^node.value;
if(value>result){
result = value;
}
dfs(node.left,value);
dfs(node.right,value);
}
} 
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