Google算法面试【面试】
code1
https://www.bilibili.com/video/BV1yC4y127rc
给你一些街区和你喜欢去的地方
街区中包含是否有没有你所喜欢去的地方
返回你可以到达这些地方的最大距离中值最小的街道下标
Blocks =[
{
"gym": false,
"school": true
"store": false,
},
{
"gym": true,
"school": false
"store": false
},
{
"gym": true,
"school": true
"store": false,
},
{
"gym": false,
"school": true
"store": false
},
{
"gym": false,
"school": true,
"store": true
}
Reqs =["gym","school", "store"]Answer：3代码
package google;
import java.util.Arrays;
/*
https://www.bilibili.com/video/BV1yC4y127rc
给你一些街区和你喜欢去的地方
街区中包含是否有没有你所喜欢去的地方
返回你可以到达这些地方的最大距离中最小的街道下标
Answer：3
Blocks =[
{
"gym": false,
"school": true
"store": false,
},
{
"gym": true,
"school": false
"store": false
},
{
"gym": true,
"school": true
"store": false,
},
{
"gym": false,
"school": true
"store": false
},
{
"gym": false,
"school": true,
"store": true
}
Reqs =["gym","school", "store"]
//0 * 0 * * 1 0 4 4
//1 0 1 * * 0 1 3 3
//2 0 0 * * 0 0 2 2
//3 1 0 * * 1 0 1 1
//4 2 0 0 2
*/
public class Main1 {
public static void main(String[] args) {
// ArrayList<HashMap<String,Boolean>> blocks=new ArrayList<>();
// ArrayList<String> reqs=new ArrayList<>();
//简单数据表示
int[][] blocks={
{0,1,0},
{1,0,0},
{1,1,0},
{0,1,0},
{0,1,1}
};
int[] reqs={0,1,2};
int n=blocks.length;
int m=blocks[0].length;
//第m位表示到所需地点的最大距离
int[][] dp=new int[n][m+1];
for (int i = 0; i < n; i++) {
Arrays.fill(dp[i],Integer.MAX_VALUE);
}
//单独处理第0个
for (int j=0;j<m;j++){
if(blocks[0][j]==1){
dp[0][j]=0;
}
}
//从左到右
for (int i=1;i<n;i++){
dp[i][m]=0;
for(int j=0;j<m;j++){
if(blocks[i][j]==1){
dp[i][j]=0;
}else {
if(dp[i-1][j]!=Integer.MAX_VALUE){
dp[i][j]=Math.min(dp[i][j],dp[i-1][j]+1);
}
}
dp[i][m]=Math.max(dp[i][m],dp[i][j]);
}
}
//从右到左
for (int i=n-2;i>=0;i--){
dp[i][m]=0;
for(int j=0;j<m;j++){
if(blocks[i][j]==1){
dp[i][j]=0;
}else {
if(dp[i+1][j]!=Integer.MAX_VALUE){
dp[i][j]=Math.min(dp[i][j],dp[i+1][j]+1);
}
}
dp[i][m]=Math.max(dp[i][m],dp[i][j]);
}
}
for (int i = 0; i < n; i++) {
System.out.println(Arrays.toString(dp[i]));
}
int ans=dp[0][m];
int ansIndex=0;
for (int i = 1; i < n; i++) {
if(dp[i][m]<ans){
ans=dp[i][m];
ansIndex=i;
}
}
System.out.println(ansIndex);
}
}code2
https://www.bilibili.com/video/BV1wM411Z7ZQ
0代表海洋，1代表陆地
删除和边界邻接的岛屿
[
[1,0,0,0,0,0],
[0,1,0,1,1,1],
[0,0,1,0,1,0],
[1,1,0,0,1,0],
[1,0,1,1,0,0],
[1,0,0,0,0,1]
]
[
[0,0,0,0,0,0],
[0,1,0,0,0,0],
[0,0,1,0,0,0],
[0,0,0,0,0,0],
[0,0,1,1,0,0],
[0,0,0,0,0,0]
]代码
package google;
import java.util.Arrays;
/*
https://www.bilibili.com/video/BV1wM411Z7ZQ
0代表海洋，1代表陆地
删除和边界邻接的岛屿
[
[1,0,0,0,0,0],
[0,1,0,1,1,1],
[0,0,1,0,1,0],
[1,1,0,0,1,0],
[1,0,1,1,0,0],
[1,0,0,0,0,1]
]
[
[0,0,0,0,0,0],
[0,1,0,0,0,0],
[0,0,1,0,0,0],
[0,0,0,0,0,0],
[0,0,1,1,0,0],
[0,0,0,0,0,0]
]
*/
public class Main2 {
public static void main(String[] args) {
int[][] martix={
{1,0,0,0,0,0},
{0,1,0,1,1,1},
{0,0,1,0,1,0},
{1,1,0,0,1,0},
{1,0,1,1,0,0},
{1,0,0,0,0,1}
};
int[][] res=removeIslands(martix);
for (int[] r:res) {
System.out.println(Arrays.toString(r));
}
}
static int n;
static int m;
//队列
static int[][] queue;
static int l;
static int r;
//方向数组(i,i+1) 下，左，上，右
static int[] moved={1,0,-1,0,1};
//也可以用二维数组表示
//{{1,0},{-1,0},{0,1},{0,-1}}
//广度优先遍历
private static int[][] removeIslands(int[][] martix) {
//初始化
n=martix.length;
m=martix[0].length;
//记录需要删除的岛屿坐标，代表删除的为1
int[][] removed=new int[n][m];
//数组代替队列
queue=new int[n*m][2];
l=r=0;
//队列中添加边界为1的岛屿
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if(i==0||j==0||i==n-1||j==m-1){
if(martix[i][j]==1){
queue[r++]=new int[]{i,j};
}
}
}
}
//队列不为空
while (l<=r){
int[] cur =queue[l++];
removed[cur[0]][cur[1]]=1;
for (int i = 0; i < 4; i++) {
int nextX= cur[0]+moved[i];
int nextY= cur[1]+moved[i+1];
//不出边界
if (nextX>=0&&nextX<n&&nextY>=0&&nextY<m){
//没有被访问的1
if(removed[nextX][nextY]!=1&&martix[nextX][nextY]==1) {
queue[r++] = new int[]{nextX, nextY};
}
}
}
}
//返回删除之后的岛屿只需要异或就行
for(int i=0;i<n;i++){
for (int j=0;j<m;j++){
martix[i][j]^=removed[i][j];
}
}
return martix;
}
}code3
https://www.bilibili.com/video/BV1YN4y1b7mC
电话表入下
---------------------
| 1 | 2 | 3 |
| | abc | def |
---------------------
| 4 | 5 | 6 |
| ghi | jkl | mno |
---------------------
| 7 | 8 | 9 |
| pqrs | tuv | wxyz |
---------------------
| | 0 | |
| | | |
---------------------给你一个电话号码，和一些单词
找出哪些单词在电话号码中出现
phoneNumber="3662277"
words = ["foo", "bar", "baz", "foobar", "emo", "cap", "car", "cat"]
Output: ["bar", "cap", "car", "emo", "foo", "foobar"]代码
package google;
import java.util.ArrayList;
/*
https://www.bilibili.com/video/BV1YN4y1b7mC
电话表入下
---------------------
| 1 | 2 | 3 |
| | abc | def |
---------------------
| 4 | 5 | 6 |
| ghi | jkl | mno |
---------------------
| 7 | 8 | 9 |
| pqrs | tuv | wxyz |
---------------------
| | 0 | |
| | | |
---------------------
给你一个电话号码，和一些单词
找出哪些单词在电话号码中出现
phoneNumber="3662277"
words = ["foo", "bar", "baz", "foobar", "emo", "cap", "car", "cat"]
Output: ["bar", "cap", "car", "emo", "foo", "foobar"]
*/
public class Main3 {
//字母对应数字
static int[] chars={2,2,2,3,3,3,4,4,4,5,5,5,6,6,6,7,7,7,7,8,8,8,9,9,9,9};
public static void main(String[] args) {
String phoneNumber="3662277";
String[] words = {"foo", "bar", "baz", "foobar", "emo", "cap", "car", "cat"};
int m= words.length;
//把单词表转为号码字符串就好了
String[] wordNums=new String[m];
for (int i = 0; i < m; i++) {
wordNums[i]="";
for (int j = 0; j < words[i].length(); j++) {
wordNums[i]+=(chars[ words[i].charAt(j)-'a']);
}
}
ArrayList<String> ans=new ArrayList<>();
for (int i=0;i<m;i++){
if(phoneNumber.contains(wordNums[i])){//用java API 字符串查找
ans.add(words[i]);
}
}
System.out.println(ans);
}
//都转为数字，构建前缀树查找
// int n=phoneNumber.length();
// int m= words.length;
// int[] phone=new int[n];
// for (int i = 0; i < n; i++) {
// phone[i]=phoneNumber.charAt(i)-'0';
// }
// System.out.println(Arrays.toString(phone));
//
// ArrayList<Integer>[] wordNums=new ArrayList[m];
// for (int i = 0; i < m; i++) {
// wordNums[i]=new ArrayList<Integer>();
// for (int j = 0; j < words[i].length(); j++) {
// wordNums[i].add(chars[ words[i].charAt(j)-'a']);
// }
// }
//
// for (ArrayList<Integer> word:wordNums) {
// System.out.println(word);
// }
}code4
https://www.bilibili.com/video/BV1nb4y1G7Pj
给一个PI若干位s
给一个喜欢的数组favArr
求在s中加入最少得空格数，使得划分后的词都出现在favArr中
Sample Input:
- 3141592653589793238462643383279
- ['314','49','9001',15926535897','14','9323','8462643383279','4','793']
Sample Output:
- 3(314 15926535897 9323 8462643383279)package google;
import java.util.Arrays;
import java.util.HashMap;
/*
https://www.bilibili.com/video/BV1nb4y1G7Pj
给一个PI若干位s
给一个喜欢的数组favArr
求在s中加入最少得空格数，使得都出现在favArr中
Sample Input:
- 3141592653589793238462643383279
- ['314','49','9001',15926535897','14','9323','8462643383279','4','793']
Sample Output:
- 3(314 15926535897 9323 8462643383279)
*/
public class Main1227 {
public static void main(String[] args) {
String s="3141592653589793238462643383279";
String[] favArr={"314","49","9001","15926535897","14","9323","8462643383279","4","793"};
// String s="31415926";
// String[] favArr={"3","141","5926"};
int res1=minSpaces1(s,favArr);
System.out.println(res1);
int res2=minSpaces2(s,favArr);
System.out.println(res2);
}
static HashMap<String,Boolean> exists=new HashMap<>();
static char[] pi;
static int[] dp;
static int n;
//时间复杂度O(n^2)
//空间复杂度
//exists表O(n)
//dp表 O(n)
//尝试递归
static int minSpaces1(String s,String[] favArr){
Main1227.pi=s.toCharArray();
n=s.length();
dp=new int[n];
Arrays.fill(dp,-1);
for (String a:favArr){
exists.put(a,true);
}
//空格数=词数-1
return check(0)-1;
}
//最小的划分词数
//空格树=词数-1
//s[pos...]的最小划分数
//不存在返回Integer.MAX_VALUE
static int check(int pos){
if(pos==n){
return 0; //base case
}
if(dp[pos]!=-1){
return dp[pos];
}
int ans=Integer.MAX_VALUE;
String cur="";
for(int j=pos;j<n;j++){
cur+=pi[j];
if(exists.getOrDefault(cur,false)){
int other=check(j+1);
if(other!=Integer.MAX_VALUE){
ans=Math.min(ans,1+other);
}
}
}
dp[pos]=ans;
return ans;
}
//时间复杂度O(n^2)
//空间复杂度
//exists表O(n)
//dp表O(n)
//严格位置依赖的动态规划
static int minSpaces2(String s,String[] favArr){
char[] pi=s.toCharArray();
int n=pi.length;
int[] dp=new int[n+1];
HashMap<String,Boolean> exists=new HashMap<>();
for (String a:favArr){
exists.put(a,true);
}
dp[n]=0;
for(int i=n-1;i>=0;i--){
String cur="";
int ans=Integer.MAX_VALUE;
for (int j = i; j < n; j++) {
cur+=pi[j];
if(exists.getOrDefault(cur,false)){
int other=dp[j+1];
if(other!=Integer.MAX_VALUE){
ans=Integer.min(ans,1+other);
}
}
}
dp[i]=ans;
}
//空格数=词数-1
return dp[0]-1;
}
//空间压缩不好压缩
}2023-12-27 15:26:10
