87 C++ - 常用遍历算法

/*
    遍历算法 遍历容器元素
  @param beg 开始迭代器
  @param end 结束迭代器
  @param _callback  函数回调或者函数对象
  @return 函数对象
*/
for_each(iterator beg, iterator end, _callback);
/*
  transform算法 将指定容器区间元素搬运到另一容器中
  注意 : transform 不会给目标容器分配内存，所以需要我们提前分配好内存
  @param beg1 源容器开始迭代器
  @param end1 源容器结束迭代器
  @param beg2 目标容器开始迭代器
  @param _cakkback 回调函数或者函数对象
  @return 返回目标容器迭代器
*/
transform(iterator beg1, iterator end1, iterator beg2, _callbakc)

/*
template<class _InIt,class _Fn1> inline
void for_each(_InIt _First, _InIt _Last, _Fn1 _Func)
{
  for (; _First != _Last; ++_First)
    _Func(*_First);
}
*/
//普通函数
void print01(int val){
  cout << val << " ";
}
//函数对象
struct print001{
  void operator()(int val){
    cout << val << " ";
  }
};
//for_each算法基本用法
void test01(){
  vector<int> v;
  for (int i = 0; i < 10;i++){
    v.push_back(i);
  }
  //遍历算法
  for_each(v.begin(), v.end(), print01);
  cout << endl;
  for_each(v.begin(), v.end(), print001());
  cout << endl;
}
struct print02{
  print02(){
    mCount = 0;
  }
  void operator()(int val){
    cout << val << " ";
    mCount++;
  }
  int mCount;
};
//for_each返回值
void test02(){
  vector<int> v;
  for (int i = 0; i < 10; i++){
    v.push_back(i);
  }
  print02 p = for_each(v.begin(), v.end(), print02());
  cout << endl;
  cout << p.mCount << endl;
}
struct print03 : public binary_function<int, int, void>{
  void operator()(int val,int bindParam) const{
    cout << val + bindParam << " ";
  }
};
//for_each绑定参数输出
void test03(){
  vector<int> v;
  for (int i = 0; i < 10; i++){
    v.push_back(i);
  }
  for_each(v.begin(), v.end(), bind2nd(print03(),100));
}

//transform 将一个容器中的值搬运到另一个容器中
/*
  template<class _InIt, class _OutIt, class _Fn1> inline 
  _OutIt _Transform(_InIt _First, _InIt _Last,_OutIt _Dest, _Fn1 _Func)
  { 
    for (; _First != _Last; ++_First, ++_Dest)
      *_Dest = _Func(*_First);
    return (_Dest);
  }
  template<class _InIt1,class _InIt2,class _OutIt,class _Fn2> inline
  _OutIt _Transform(_InIt1 _First1, _InIt1 _Last1,_InIt2 _First2, _OutIt _Dest, _Fn2 _Func)
  { 
    for (; _First1 != _Last1; ++_First1, ++_First2, ++_Dest)
      *_Dest = _Func(*_First1, *_First2);
    return (_Dest);
  }
*/
struct transformTest01{
  int operator()(int val){
    return val + 100;
  }
};
struct print01{
  void operator()(int val){
    cout << val << " ";
  }
};
void test01(){
  vector<int> vSource;
  for (int i = 0; i < 10;i ++){
    vSource.push_back(i + 1);
  }
  //目标容器
  vector<int> vTarget;
  //给vTarget开辟空间
  vTarget.resize(vSource.size());
  //将vSource中的元素搬运到vTarget
  vector<int>::iterator it = transform(vSource.begin(), vSource.end(), vTarget.begin(), transformTest01());
  //打印
  for_each(vTarget.begin(), vTarget.end(), print01()); cout << endl;
}
//将容器1和容器2中的元素相加放入到第三个容器中
struct transformTest02{
  int operator()(int v1,int v2){
    return v1 + v2;
  }
};
void test02(){
  vector<int> vSource1;
  vector<int> vSource2;
  for (int i = 0; i < 10; i++){
    vSource1.push_back(i + 1);  
  }
  //目标容器
  vector<int> vTarget;
  //给vTarget开辟空间
  vTarget.resize(vSource1.size());
  transform(vSource1.begin(), vSource1.end(), vSource2.begin(),vTarget.begin(), transformTest02());
  //打印
  for_each(vTarget.begin(), vTarget.end(), print01()); cout << endl;
}