将std :: map数据复制到另一个地图 [英] Copy std::map data to another map

问题描述

我有一个像这样定义的地图

  struct A 
 {
 int A; 
 int B; 
}; 
 typedef map< int，A>一张地图; 
  

然后我有 Amap1 它到 Amap2

  A a .... 
 Amap Amap1，Amap2; 
 Amap1 [1] = a1; 
 Amap1 [2] = a2; 
 Amap1 [3] = a3; 
 Amap2.insert（Amap1.begin（），Amap1.end（））; 
 

有时这个工作正常，有时这只会复制键和值0.在这里我的错误？

解决方案

首先， std :: map stl :: map ：）

第二次将一张地图复制到另一张地图可以使用operator =

 地图< X，Y> mp1; 
 //用数据填充mp1 
 map< X，Y> mp2（mp1）; // mp2是mp1的副本（通过拷贝构造）
 map< X，Y> mp3; 
 mp3 = mp2; // mp3也是mp2的副本（通过复制赋值）
  

I have a map that's defined like this

 struct A
 {
  int A;
  int B;
 };
 typedef map<int,A> Amap;

Then I have Amap1 and I want copy it to Amap2

 A a....;
 Amap Amap1,Amap2;
 Amap1[1]=a1;
 Amap1[2]=a2;
 Amap1[3]=a3;
 Amap2.insert(Amap1.begin(), Amap1.end());

Sometimes this work properly, sometimes this copies only the keys and the value 0. Where is my mistake here?

解决方案

First of all, it's std::map, not stl::map :)

And second copying one map to another can be done with operator = or the copy constructor.

E.g

map<X, Y> mp1; 
//fill mp1 with data
map<X, Y> mp2(mp1); //mp2 is a copy of mp1 (via copy-construction)
map<X, Y> mp3;
mp3 = mp2; // mp3 is also a copy of mp2 (via copy-assignment)

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