K个可变长度向量的循环迭代器

给定K个向量，任务是设计一个循环迭代器，以循环方式打印这些向量的元素。例如： v1 = {1、2、3}，v2 = {4、5、6}和v3 = {7、8、9}，则输出应为1、4、7、2、5、8、3 ，6和9 。

例子：

Input: v1 = {1, 2}, v2 = {3, 4, 5}, v3 = {6}
Output: 1 3 6 2 4 5

Input: v1 = {1, 2}, v2 = {3, 4}
Output: 1 3 2 4

方法：创建两个数组，一个数组将存储每个向量的开始迭代器，另一个数组将存储每个向量的结束迭代器。然后以循环方式打印矢量的内容。由于矢量的长度可以变化，因此请跳过所有已打印其元素的矢量。

下面是上述方法的实现：

// C++ implementation of the approach
#include 
using namespace std;
  
// Class for the cyclic iterator
class Iterator {
public:
    Iterator(vector& a1, vector& a2,
             vector& a3, vector& a4, int k);
    int numOfVectors;
    int currIndex;
  
    // Vectors to store the starting and the
    // ending iterators for each of the vector
    vector::iterator> iStart;
    vector::iterator> iEnd;
  
    // Function that returns true if
    // there are elements left to print
    bool hasNext();
  
    // Function that returns the next
    // element in a cyclic manner
    int next();
};
  
// Function that returns true if
// there are elements left to print
bool Iterator::hasNext()
{
  
    // If iterator of any vector has not
    // reached the end then return true
    for (int i = 0; i < numOfVectors; i++) {
        if (iStart[i] != iEnd[i])
            return true;
    }
    return false;
}
  
// Function that returns the next
// element in a cyclic manner
int Iterator::next()
{
    int elem = 0;
    if (iStart[currIndex] != iEnd[currIndex]) {
        elem = *iStart[currIndex]++;
        currIndex = (currIndex + 1) % numOfVectors;
        return elem;
    }
    else {
        currIndex = (currIndex + 1) % numOfVectors;
        return next();
    }
    return elem;
}
  
// Initialise object of the Iterator class
Iterator::Iterator(vector& a1, vector& a2,
                   vector& a3, vector& a4, int k)
{
    numOfVectors = k;
    iStart.resize(numOfVectors);
    iEnd.resize(numOfVectors);
  
    // Store begin iterators
    iStart[0] = a1.begin();
    iStart[1] = a2.begin();
    iStart[2] = a3.begin();
    iStart[3] = a4.begin();
  
    // Store ending iterators
    iEnd[0] = a1.end();
    iEnd[1] = a2.end();
    iEnd[2] = a3.end();
    iEnd[3] = a4.end();
  
    // CurrIndex denotes the vector's index
    // whose element is to be printed next
    currIndex = 0;
}
  
// Function to print the elements in a cyclic manner
void iterateCyclic(vector& a1, vector& a2,
                   vector& a3, vector& a4, int k)
{
  
    // Initialise the iterator
    Iterator it(a1, a2, a3, a4, k);
  
    // Print all the element
    // in a cyclic fashion
    while (it.hasNext()) {
        cout << it.next() << " ";
    }
}
  
// Driver code
int main()
{
    // Initialize the vectors
    vector a1;
    a1.push_back(1);
    a1.push_back(2);
    a1.push_back(3);
  
    vector a2;
    a2.push_back(4);
    a2.push_back(5);
    a2.push_back(6);
    a2.push_back(7);
  
    vector a3;
    a3.push_back(8);
    a3.push_back(9);
  
    vector a4;
    a4.push_back(10);
    a4.push_back(11);
  
    // Print the elements in a cyclic fashion
    iterateCyclic(a1, a2, a3, a4, 4);
  
    return 0;
}

输出：

1 4 8 10 2 5 9 11 3 6 7