地图，但仅给出一行值

本文介绍了地图，但仅给出一行值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

你好 我正在使用网络模拟器(ns2)进行c ++，但是我在c ++中是一个全新的人. 我想读取每个节点的数据并保存在map中.我没有使用数组，因为到那时将不会读取所有节点；数据的大小未知. 我发出这样的命令

Hello I''m doing c++ with network simulator(ns2)but I''m totally new in c++. I want to read data for each node and keep in map.I didn''t use array as all nodes will not be read for that time;the size of data is not known. I give a command like this

void Update(){ int q=0.5; int NodeId=ra_addr ; CurNode= (MobileNode*) (Node::get_node_by_address(ra_addr_)); map_table(NodeId,iEnergy ); } void map_table(int node_id,double Eg){ map<int, double > mymap; map<int, double > ::iterator it; it=mymap.find(node_id); if(it == mymap.end())mymap.insert(map<int,double>::value_type(node_id,Eg)); else mymap[node_id]=Eg; for( map<int, double > ::iterator ii=mymap.begin(); ii!=mymap.end(); ii++) { cout << (*ii).first << ": " << (*ii).second << endl; }

当我打印时，它只包含一个node_id，不是全部.我的想法是检查id是否在地图中，更新新数据，例如，我尝试在头文件中声明map也给出相同的结果. br/> 结果应该像 节点||数据 1 3.45 2 4.25 6 1.23 预先谢谢你 pare

when i print,it contain only one node_id,not all.My idea is to check id if it''s in the map,update a new data,Eg.i try to declare map in header file also give the same result. the result should be like node || data 1 3.45 2 4.25 6 1.23 thank you in advance pare

推荐答案

问题是mymap对于map_table方法是本地的.因此，每次向其中添加内容时，它都会是第一个. 确保mymap在方法之外声明，或正在传递到方法中. 这样的事情可能会起作用； The problem is that mymap is local to the map_table method. So every time you add something to it it''s going to be the first one. Make sure mymap is declared outside of the method, or is being passed in to the method. Something like this might work; #include <iostream> #include <map> using namespace std; map<int, double> mymap; void map_table(int node_id, double Eg) { map<int, double>::iterator it = mymap.find(node_id); if(it == mymap.end()) mymap.insert(map<int,double>::value_type(node_id,Eg)); else mymap[node_id]=Eg; for(map<int, double>::iterator i = mymap.begin(); i != mymap.end(); ++i) { cout << (*i).first << ": " << (*i).second << endl; } } int main() { map_table(1, 40.0); cout << "---------------------------" << endl; map_table(2, 42.0); cout << "---------------------------" << endl; map_table(1, 43.0); cout << "---------------------------" << endl; map_table(3, 40.0); return 0; }

打印:

That prints:

1: 40 --------------------------- 1: 40 2: 42 --------------------------- 1: 43 2: 42 --------------------------- 1: 43 2: 42 3: 40

希望这会有所帮助， 弗雷德里克(Fredrik)

Hope this helps, Fredrik

感谢您的回复.我确实按照您的指示进行了尝试，并得到了这样的结果 thanks for ur reply.I did try as you told and got result like this print data in map 0: 190.809 1: 91.8829 4: 58.4821 print data in map 1: 91.8829 2: 2.40965 3: 276.987 4: 58.4821 print data in map 0: 190.809 2: 2.40965 3: 276.987 4: 58.4821 print data in map 0: 190.809 1: 91.8829 3: 276.987

似乎缺少一些ID.

seems like some id is missing.

请在引用此映射的位置共享代码，我想您可能会以其他方式从此映射中删除实体，具体取决于您的网络模拟拓扑变化时节点的数量. Please share the code where you are referencing this map , I guess you might be deleting the enrties from this map in some other flow, depending on your network simulation of nodes as the topology changes.