c++利用stl set_difference对车辆进出区域进行判定

核心代码

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;
struct _AREA_VECTOR_STRUCT
{
  int nAreaType;//区域类型
  int nAreaID;//区域ID
}; 

void CtestDlg::OnBnClickedButton2()
{
  vector<_AREA_VECTOR_STRUCT> structAreaHistory;//车辆上一次所在区域
  vector<_AREA_VECTOR_STRUCT> structAreaNow;//车辆本次所在区域
  vector<_AREA_VECTOR_STRUCT> OutStructAreaVector;//输出区域 

  _AREA_VECTOR_STRUCT structVehicle; 

  //模拟上一次车辆所在的区域集合
  structVehicle.nAreaType = 2;
  structVehicle.nAreaID = 0x45;
  structAreaHistory.push_back(structVehicle);
  structVehicle.nAreaID = 0x7A;
  structAreaHistory.push_back(structVehicle);
  structVehicle.nAreaID = 0x88;
  structAreaHistory.push_back(structVehicle); 

  structVehicle.nAreaType = 3;
  structVehicle.nAreaID = 0x55;
  structAreaHistory.push_back(structVehicle);
  structVehicle.nAreaID = 0x88;
  structAreaHistory.push_back(structVehicle); 

  //模拟本次车辆所在的区域集合
  structVehicle.nAreaType = 2;
  structVehicle.nAreaID = 0x88;
  structAreaNow.push_back(structVehicle);
  structVehicle.nAreaID = 0x45;
  structAreaNow.push_back(structVehicle);
  structVehicle.nAreaID = 0x11;
  structAreaNow.push_back(structVehicle); 

  structVehicle.nAreaType = 3;
  structVehicle.nAreaID = 0x55;
  structAreaNow.push_back(structVehicle); 

  //排序，先按区域类型排序，再按区域ID排序
  sort(structAreaHistory.begin(), structAreaHistory.end(),[] (_AREA_VECTOR_STRUCT structArea1, _AREA_VECTOR_STRUCT structArea2)->bool
  {
    if(structArea1.nAreaType != structArea2.nAreaType)
      return structArea1.nAreaType < structArea2.nAreaType;
    else
      return structArea1.nAreaID < structArea2.nAreaID;
  });
  sort(structAreaNow.begin(), structAreaNow.end(),[] (_AREA_VECTOR_STRUCT structArea1, _AREA_VECTOR_STRUCT structArea2)->bool
  {
    if(structArea1.nAreaType != structArea2.nAreaType)
      return structArea1.nAreaType < structArea2.nAreaType;
    else
      return structArea1.nAreaID < structArea2.nAreaID;
  }); 

  int a = 0; 

  //求差，结果为离开区域的集合（出区域）
  set_difference(structAreaHistory.begin(), structAreaHistory.end(), structAreaNow.begin(), structAreaNow.end(), back_inserter(OutStructAreaVector),
    [](_AREA_VECTOR_STRUCT structArea1, _AREA_VECTOR_STRUCT structArea2)->bool
  {
    if(structArea1.nAreaType != structArea2.nAreaType)
      return structArea1.nAreaType < structArea2.nAreaType;
    else
      return structArea1.nAreaID < structArea2.nAreaID;
  }); 

  if(OutStructAreaVector.size() != 0)
  {
    TRACE("出");
  } 

  OutStructAreaVector.clear();//先清空 

  //反过来求差，结果为新进入的区域集合（新进区域）
  set_difference(structAreaNow.begin(), structAreaNow.end(), structAreaHistory.begin(), structAreaHistory.end(), back_inserter(OutStructAreaVector),
    [](_AREA_VECTOR_STRUCT structArea1, _AREA_VECTOR_STRUCT structArea2)->bool
  {
    if(structArea1.nAreaType != structArea2.nAreaType)
      return structArea1.nAreaType < structArea2.nAreaType;
    else
      return structArea1.nAreaID < structArea2.nAreaID; 

  }); 

  if(OutStructAreaVector.size() != 0)
  {
    TRACE("重新进");
  }
}