Question

我正在尝试创建一个方法，该方法采用ArrayList并将其中的所有内容加倍。例如，如果ArrayList单词存储了[“ hello”，“ there”]，则应输出[“ Hello”，“ Hello”，“ there”，“ there”]。我已经做出了一种我认为应该可行的方法，但是没有奏效。谁能告诉我我错了哪里？我将不胜感激！我的代码在下面。

public ArrayList<String> doubleList(ArrayList<String> words) {
    ArrayList<String> newWords = new ArrayList<String>();
    for (int i = 0; i < words.size(); i++) {
        newWords.add(words.get(i));
        newWords.add(words.get(i));
    }
    return newWords;
}

Answer 1

好吧，我尝试运行您的方法，并且效果很好。

import java.util.ArrayList;

public class Test {

    public static void main(String[] args) {
        ArrayList<String> words = new ArrayList<>();
        words.add("a");
        words.add("b");
        words.add("c");
        ArrayList<String> doubledList = doubleList(words);
        System.out.println(doubledList);
    }

    public static ArrayList<String> doubleList(ArrayList<String> words) {
        ArrayList<String> newWords = new ArrayList<>();
        for (int i = 0; i < words.size(); i++) {
            newWords.add(words.get(i));
            newWords.add(words.get(i));
        }
        return newWords;
    }
}

我得到的结果如下：

[a，a，b，b，c，c]

Answer 2

我怀疑您的网站可能不喜欢您正在创建新存储。我们如何像这样进行一些更改？

$ cat transfer.cu
#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include "transfer.h"
#include <iostream>
#include <cstdio>
#include <thrust/copy.h>
#include <vector>

__global__ void k(float *data, size_t ds){
  for (int i = 0; i < ds; i++) printf("%f,", data[i]);
}

// thrust vectors (global)
std::vector<thrust::host_vector<float> > trianglethrust_host;
std::vector<thrust::device_vector<float> > trianglethrust_device;

void trianglesToGPU_thrust(const float *mesh, float** triangles) {
//create vectors
  trianglethrust_host.resize(1);
  trianglethrust_device.resize(1);

// fill host vector
size_t i = 0;
  while (mesh[i] != 0.0f) {
    trianglethrust_host[0].push_back(mesh[i++]);
  }
// copy to GPU by assigning host vector to device vector, like in the Thrust documentation
  trianglethrust_device[0] = trianglethrust_host[0];
// save raw pointer
  *triangles = (float*)thrust::raw_pointer_cast(trianglethrust_device[0].data());
}

void do_global_work(float** triangles){

  std::cout << "from device vector:" << std::endl;
  thrust::copy(trianglethrust_device[0].begin(), trianglethrust_device[0].end(), std::ostream_iterator<float>(std::cout, ","));
  std::cout << std::endl << "from kernel:" << std::endl;
  k<<<1,1>>>(*triangles, trianglethrust_device[0].size());
  cudaDeviceSynchronize();
  std::cout << std::endl;
}

void finish(){
  trianglethrust_host.clear();
  trianglethrust_device.clear();
}
$ nvcc -c transfer.cu
$ g++ -o test main.o transfer.o -L/usr/local/cuda/lib64 -lcudart
$ ./test
from device vector:
0.1,0.2,0.3,
from kernel:
0.100000,0.200000,0.300000,
$

如何制作一个新的ArrayList并复制其中的所有内容？

2 个答案: