计算三胞胎-首次进场 [英] Count triplets - First Approch
问题描述
我正在HackerRank上进行此练习:
I'm doing this exercise on HackerRank:
为您提供了一个数组，您需要查找索引(i，j，k)的三元组数，以使在给定的公共比率r和i<时，这些索引处的元素呈几何级数.&
You are given an array and you need to find number of triplets of indices (i, j, k) such that the elements at those indices are in geometric progression for a given common ratio r and i < j < k.
完整练习: https://www.hackerrank.com/challenges/count-triplets-1/问题我的编译器有问题.这是代码:
Full exercise: https://www.hackerrank.com/challenges/count-triplets-1/problem I have problems with compiler. This is code:
import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;
public class Solution {
// Complete the countTriplets function below.
static long countTriplets(List<Long> arr, long r) {
int counter = 0;
for (int i = 0; i < arr.length() - 2; i++) {
for (int j = i + 1; j < arr.length() - 1; j++) {
if (arr[j] - arr[i] == r) {
for (int k = j + 1; k < arr.length(); k++) {
if (arr[k] - arr[j] == r) {
System.out.println("(" + arr[i] + "," + arr[j] + "," + arr[k] + ")");
counter++;
break;
}
}
}
}
}
;
return counter;
}
public static void main(String[] args) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
String[] nr = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");
int n = Integer.parseInt(nr[0]);
long r = Long.parseLong(nr[1]);
List<Long> arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" ")).map(Long::parseLong)
.collect(toList());
long ans = countTriplets(arr, r);
bufferedWriter.write(String.valueOf(ans));
bufferedWriter.newLine();
bufferedReader.close();
bufferedWriter.close();
}
}
我有此错误:
Solution.java:19: error: cannot find symbol
for (int i = 0; i < arr.length() -2; i++){
^
symbol: method length()
location: variable arr of type List<Long>
Solution.java:20: error: cannot find symbol
for(int j = i + 1; j < arr.length() -1; j++){
^
symbol: method length()
location: variable arr of type List<Long>
Solution.java:21: error: array required, but List<Long> found
if(arr[j] - arr[i] == r){
^
Solution.java:21: error: array required, but List<Long> found
if(arr[j] - arr[i] == r){
^
Solution.java:22: error: cannot find symbol
for(int k = j + 1; k < arr.length(); k++){
^
symbol: method length()
location: variable arr of type List<Long>
Solution.java:23: error: array required, but List<Long> found
if(arr[k] - arr[j] == r){
^
Solution.java:23: error: array required, but List<Long> found
if(arr[k] - arr[j] == r){
^
Solution.java:24: error: array required, but List<Long> found
System.out.println("(" +arr[i] + "," +arr[j] + "," +arr[k] +")");
^
Solution.java:24: error: array required, but List<Long> found
System.out.println("(" +arr[i] + "," +arr[j] + "," +arr[k] +")");
^
Solution.java:24: error: array required, but List<Long> found
System.out.println("(" +arr[i] + "," +arr[j] + "," +arr[k] +")");
^
10 errors
(我从编程开始，所以我不知道代码是否正确)
(I'm starting out with programming, so I don't know if the code is correct)
=============================================================================
=============================================================================
更新:我没有错误，但每个测试用例返回0.
UPDATE: I don't have errors, but return 0 for each test cases.
public class Solution {
// Complete the countTriplets function below.
static long countTriplets(List<Long> arr, long r) {
// Long[] a = arr.toArray();
int counter = 0;
for (int i = 0; i < arr.size() - 2; i++) {
for (int j = i + 1; j < arr.size() - 1; j++) {
if (arr.get(j) - arr.get(i) == r) {
for (int k = j + 1; k < arr.size(); k++) {
if (arr.get(k) - arr.get(j) == r) {
System.out.println("(" + arr.get(i) + "," + arr.get(j) + "," + arr.get(k) + ")");
counter++;
break;
}
}
}
}
}
return counter;
}
}
推荐答案
您的问题是您要混淆两个相似但最终是非常不同的概念.
Your problem is that you are mixing up two similar, but in the end: very different concepts.
static long countTriplets(List<Long> arr, long r) {
似乎您想将 arr 视为 array .因为稍后您将使用数组访问语法 arr [someIndex] .
It seems you want to think of arr as of array. Because you later use the array access syntax arr[someIndex].
但是，您并没有将其声明为 array .您在那里有一个列表.
But well, you didn't declare it as array. You have a List there.
然后，您必须使用以下内容:
Then you have to use things like:
someList.getSize()
获取列表的 length ，或
someList.get(someIndex)
获取该列表中的特定元素.
to acquire a specific element in that list.
但是真正的答案是:当您不了解这样的基本基本知识时，然后从某个地方获取一些代码，然后将其转换为hackerrank，这不是您现在应该做的.
But the real answer is: when you don't understand such fundamental basic stuff, then fetching some code from somewhere, to turn it to hackerrank isn't what you should be doing right now.
含义:为了成功编写自己的代码，以解决此类问题，您需要已经了解该语言的足够多".
Meaning: in order to successfully write your own code, to solve such exercises, you need to understand "enough" of the language already.
因此:退后一步，并获得一本有关Java的好书.并通读那本书.
Thus: step back, and get a good book about Java. And work through that book.
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