排序矩阵到第n列C ++ [英] sort matrix up to nth column c++

问题描述

如果我有一个像这样的矩阵:

If I have a matrix like this:

 4 5 3
 6 8 7
 9 5 4
 2 1 3

我只想对前两行进行排序，这样我得到:

and I want only to sort only the first two rows such that I get:

 3 4 5
 6 7 8
 9 5 4
 2 1 3

如何使用C ++ 14实现这一目标?

How can I achieve that using C++14?

推荐答案

在您期望的输出中，由于排序是行，因此标题不准确.

In your expected output, what you sort are the rows, so your title is not accurate.

以您提供的示例输出为例:

Taking the sample output you present:

实时演示

int mat[][3] = { {4, 5, 3},
                 {6, 8, 7},
                 {9, 5, 4},
                 {2, 1, 3} }; 

给出C样式的2D数组，对前2行进行排序:

Given the C-style 2D array, to sort the first 2 rows:

#include <algorithm>
//...                
std::sort(std::begin(mat[0]), std::end(mat[0]));
std::sort(std::begin(mat[1]), std::end(mat[1]));

要对整个数组进行排序，可以使用一个循环:

To sort the whole array, you would use a cycle:

for(size_t i = 0; i < sizeof(mat) / sizeof(mat[0]); i++) //deduce the number of rows
    std::sort(std::begin(mat[i]), std::end(mat[i]));

输出:

3 4 5
6 7 8
9 5 4
2 1 3

如果您想使用C ++容器(例如建议使用的向量)，或者对于固定大小的数组，请使用std::array:

If you want to use a C++ container like, let's say, a vector of vectors, as it would be recommended, or for a fixed size array a std::array:

对整个2D向量进行排序的示例(std::array的相同方法)

std::vector<std::vector<int>> mat = {
    {4, 5, 3},
    {6, 8, 7},
    {9, 5, 4},
    {2, 1, 3}};

for(size_t i = 0; i < mat.size(); i++)
    std::sort(std::begin(mat[i]), std::end(mat[i]));

如您所见，这是一种更友好的方法，即让C ++容器具有一个存储其自身大小的成员.

As you can see it's a more friendly approach give that C++ containers have a member which stores its own size.

输出:

3 4 5 
6 7 8 
4 5 9 
1 2 3 

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