排序int的多维向量？ [英] sort multidimensional vector of ints?

问题描述

相信或不，当我搜索这个，我想出了nada。

如何排序多维向量



提前感谢！

p>

C ++

  res = mysql_perform_query ，SELECT column1，column2，column3 FROM table1;）; 
 std :: vector< std :: vector& int> > myVector; 
 while（（row = mysql_fetch_row（res））！= NULL）{
 int sortedID = atoi（row [0]）; 
 std :: vector< int> tempRow; 
 tempRow.push_back（atoi（row [0]））; 
 tempRow.push_back（atoi（row [1]））; 
 tempRow.push_back（atoi（row [2]））; 
 myVector.push_back（tempRow）; 
} 
  

我要排序 myVector 由 myVector [i] [1] 降序。

std :: sort（myVector.begin（），myVector.end（），[]（const std :: vector< int>& a，const std :: vector< int& 1]> b [1];}）; //如果要按升序排序，请替换>与<


我有眼睛的代码。我还没有尝试过。
请注意，您将需要一个c ++ 11编译器来获取此代码。

编辑：语法错误修复。

编辑：测试。有用。这里是测试的代码：

  #include< iostream> 
 #include< vector> 
 #include< algorithm> 
 
 int main（）{
 std :: vector< std :: vector& int> > myVector（{{3,4,3}，{2,5,2}，{1,6,1}}）; 
 std :: sort（myVector.begin（），myVector.end（），[]（const std :: vector< int>& a，const std :: vector< int>& b） {return a [1]> b [1];}）; 
 
 std :: cout<< {; 
 for（auto i：myVector）{
 std :: cout<< [; 
 for（auto j：i）
 std :: cout<< j<< ，; 
 std :: cout<< ]，; 
} 
 std :: cout<< }<< std :: endl; 
 return 0; 
} 
  

程序输出：

$ b b

  {[1,6,1，]，[2,5,2，]，[3,4,3，]，} 
  

编辑：根据Blastfurnace的建议更改lambda函数接受const引用

Believe it or not, when I search this, I come up with nada.

How can I sort a multidimensional vector of ints by one of the "columns"?

Many thanks in advance!

C++

res = mysql_perform_query(conn, "SELECT column1, column2, column3 FROM table1;");
std::vector< std::vector< int > > myVector;
while ((row = mysql_fetch_row(res)) !=NULL){
    int rankedID = atoi(row[0]);
    std::vector< int > tempRow;
    tempRow.push_back(atoi(row[0]));
    tempRow.push_back(atoi(row[1]));
    tempRow.push_back(atoi(row[2]));
    myVector.push_back(tempRow);
}

I'd like to sort myVector by myVector[i][1] descending.

Thanks again!

解决方案

Is this what you want?

std::sort(myVector.begin(), myVector.end(), [](const std::vector< int >& a, const std::vector< int >& b){ return a[1] > b[1]; } ); //If you want to sort in ascending order, then substitute > with <.

I have eyesballed the code. I haven't tried it yet. Please notice that you will need a c++11 compiler to get this code compile.

EDIT: syntax error fixed.

EDIT: tested. It works. here is the code for the test:

#include <iostream>
#include <vector>
#include <algorithm>

int main(){
    std::vector< std::vector< int > > myVector({{3,4,3},{2,5,2},{1,6,1}});
    std::sort(myVector.begin(), myVector.end(), [](const std::vector< int >& a, const std::vector< int >& b){ return a[1] > b[1]; } );

    std::cout << "{";
    for(auto i : myVector){
        std::cout << "[";
        for(auto j : i)
            std::cout << j << ",";
        std::cout << "],";
    }
    std::cout << "}" << std::endl;
    return 0;
}

Output of the program:

{[1,6,1,],[2,5,2,],[3,4,3,],}

EDIT: changed the lambda function to accept const reference upon the suggestion of Blastfurnace

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