map | 易学教程

C++ unordered_map with char* as key

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问题 I feel exhausted when trying to use the container unordered_map with char* as the key (on Windows, I am using VS 2010). I know that I have to define my own compare function for char* , which inherits from binary_function . The following is a sample program. #include<unordered_map> #include <iostream> #include <string> using namespace std; template <class _Tp> struct my_equal_to : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return strcmp( _

Generics and inheritance: need a complex Map instance

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问题 public abstract class Mother { } public class Daughter extends Mother { } public class Son extends Mother { } I need a Map which keys are one of Daughter or Son classes, and which values are lists of objects of one of those two classes, respectively . For example: /* 1. */ map.put(Daughter.class, new ArrayList<Daughter>()); // should compile /* 2. */ map.put(Son.class, new ArrayList<Son>()); // should compile /* 3. */ map.put(Daughter.class, new ArrayList<Son>()); // should not compile /* 4.

codeWars in action（2014-05-06）

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 一、 Description: Write a small function that returns the values of an array that are not odd. All values in the array will be integers. Return the good values in the order they are given . my solution: function noOdds(values) { var arr = []; values.filter(function (val) { if (val % 2 === 0) { arr.push(val); } }); console.log(arr); return arr; } solution from web: function no_odds( values ){ // Return all non-odd values return values.filter(function(val){return val%2===0}) } 二、 Description: Fellow code warrior, we need your help! We seem to have lost one of

自己做地图

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 支持WEB、Android、IOS的地图解决方案工具链 GIS工具集 OpenGeo Suite 包含PostGIS, GeoServer, GeoWebCache, OpenLayers, 和 QGIS 地图准备 QGIS 导入、导出、编辑.shp,postgis,geotiff,geojson,dxf等多种GIS文件,给普通图片配准到地理坐标教程： http://www.qgistutorials.com/en/ DraftSight 编辑CAD文件 SketchUp 从CAD文件生成3D视图地图服务 GeoServer 地图服务发布。作为war放入Tomcat或Jetty即可使用。可发布geotiff,.shp,POSTGIS等多种GIS数据为地图。通过openlayer或QGIS浏览。 GeoWebCache 缓存地图瓦片，提高性能。已内置在最新版GeoServer中。 TileStream 把.mbtile文件发布为地图服务离线地图打包 TileMill 将geotiff,geojson,csv,shp,postgis等文件美化、打包为.mbtile瓦片地图文件,存有地图信息的sqlite文件。教程: https://www.mapbox.com/tilemill/docs

Implementing a 2D Map

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问题 I posted a Q. earlier about arrays and the replies lead me to change my game design. I'm building a 2D game map from tiles (Cells). I need to add a pen line to some cells, representing a wall you cannot pass through. This pen line is represented by Cell.TopWall, Cell.BottomWall etc etc of type boolean as shown in my code. This is my whole app so far. It draws the grid without the pen lines for walls. Take note of commented out code where i have tried different things like stating where the

Inheritance in std::map with base class as value

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问题 Here is a code: class Base { public: long index; }; class Derived : public Base { public: bool value; }; void call(map<char *, Base *> *base) { map<char *, Base *>::iterator it = base->begin(); cout << it->second->index << endl; } void test(void) { map<char *, Derived *> *d = new map<char *, Derived *>; call(d); } Compiler alerts an error: error C2664: 'call' : cannot convert parameter 1 from 'std::map<_Kty,_Ty> *' to 'std::map<_Kty,_Ty> *' 1> with 1> [ 1> _Kty=char *, 1> _Ty=Derived * 1> ] 1

Inheritance in std::map with base class as value

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Hadoop-> Mapper->How can we read only Top N rows from each file from given input path?

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问题 I am new to Hadoop, My requirement is I need to process only first 10 rows from the each input file. and how to exit mapper after reading 10 rows of each file. If anyone can provide some sample code , it would be great help. thanks in advance. 回答1: You can override the run method of your mapper, and once you've iterated the map loop 10 times you can break from the while loop. This will assume your files are not splitable, otherwise you'll get the first 10 lines from each split: @Override

Compare map key with a list of strings

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问题 can map be compare with arraylist of string in java private Map<String, String> checkInScopeLobs(Map<String, String> allLobsChkBx) { Map<String, String> inScopeLobs = new HashMap<String, String>();; for (Map.Entry<String, String> entry : allLobsChkBx.entrySet()) { if(entry.getKey().contains("1") || entry.getKey().contains("2") || entry.getKey().contains("3")){ inScopeLobs.put(entry.getKey(), entry.getValue()); } } return inScopeLobs; } is this a correct way ? 回答1: You can make use of keySet()

How to use std::string as key in stxxl::map

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问题 I am trying to use std::string as a key in the stxxl::map The insertion was fine for small number of strings about 10-100. But while trying to insert large number of strings about 100000 in it, I am getting segmentation fault. The code is as follows: struct CompareGreaterString { bool operator () (const std::string& a, const std::string& b) const { return a > b; } static std::string max_value() { return ""; } }; // template parameter <KeyType, DataType, CompareType, RawNodeSize, RawLeafSize,