[英]c++ return all of the elements that appear n times in a vector as a vector
Goal: Return all elements in vector A
that appear N times and put results in vector B
. 目标:返回向量
A
中出现N次的所有元素,并将结果放入向量B
。
Expected Result: 预期结果:
--Begin With---
Vector A=(10,20,30,30,40,50,100,50,20,100,10,10,200,300)
Do some code to return the name of elements that appear in Vector A
when N=3
Result should be Vector B=(10) //because only 10 is in vector A N=3 times.
My Attempt: I got the counts of all the elements placed into another vector but I don't have the part that can give back all of the elements that appear N
times. 我的尝试:我得到了放入另一个向量的所有元素的计数,但是我没有可以回放出现
N
次的所有元素的部分。 I'm very flexible with how it can be done if it means a speed increase . 如果它意味着速度增加,我会非常灵活地完成它 。
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <iterator> // std::back_inserter
#include <algorithm> // std::copy
int main()
{
std::vector<int> v{ 1, 2, 3, 4, 4, 3, 7, 8, 9, 10 };
std::vector<std::pair<int, int> > shows;
int target1;
int num_items1;
int size = static_cast<int>(v.size());
for(int x=0; x<size; x++)
{
target1 = v[x];
num_items1 = std::count(v.begin(), v.end(), target1);
shows.push_back(std::make_pair(target1, num_items1));
std::cout << "number: " << target1 << " count: " << num_items1 << '\n';
}
}
ACCEPTED SOLUTION TO QUESTION 接受问题的解决方案
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <iterator> // std::back_inserter
#include <algorithm> // std::copy
#include <set>
#include <map>
using namespace std;
int main()
{
std::vector<int> v{ 1, 2, 3, 4, 4, 3, 7, 8, 9, 10 };
std::vector<int> shows;
std::map<int, int> freqOfv;
for(const auto& i: v)
{
freqOfv[i]++;
}
std::set<int> s(v.begin(), v.end());
int N = 2; //Can be read from stdin as well...
for ( auto it = s.begin(); it != s.end(); it++ )
{
if(freqOfv[*it] ==N)
{
shows.push_back(*it);
}
}
for (std::vector<int>::const_iterator i = shows.begin(); i != shows.end(); ++i)
{
std::cout << *i << ' ';
}
return 0;
}
As suggested in the comments, std::map
will simplify the code: 正如评论中所建议的那样,
std::map
将简化代码:
int main()
{
std::vector<int> v{ 1, 2, 3, 4, 4, 3, 7, 8, 9, 10 };
std::map<int, int> freqOfv;
for(const auto& i: v)
freqOfv[i]++;
int N = 2; //Can be read from stdin as well...
for(const auto& i: freqOfv)
{
if(N == i.second)
std::cout << "The value " << i.first << " occurs " << N << " times." << std::endl;
}
}
This produces the following output: 这会产生以下输出:
The value 3 occurs 2 times.
The value 4 occurs 2 times.
Of course, you need #include <map>
at the beginning to use maps in your code. 当然,您需要在开头使用
#include <map>
来在代码中使用地图。
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