《C++》常用查找算法

for_each--遍历

	vector<int> v1;
	for (size_t i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	for_each(v1.begin(), v1.end(), prinvector);

find

找到与否都返回一个迭代器

	vector<int> v1;
	for (size_t i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	for_each(v1.begin(), v1.end(), prinvector);

vector<int>::iterator it = find(v1.begin(), v1.end(), 9);
	if (it==v1.end())
		cout << "没找到！" << endl;
	else
		cout << "找到了，" << *it << endl;
}

find_if

与find区别在于可以使用条件进行查找

class FindCondition
{
  bool operator()(int val)
  {
    return 10==val;
  }
};
find_if(v1.begin(),v1.end(),FindCondition());

adjaent_find

查找相邻重复元素，如果找到返回第一个元素迭代器，未找到返回end()

binary_search

二分查找容器元素，容器必须是有序的，返回bool类型

	vector<int> v1;
	for (size_t i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	bool ret = binary_search(v1.begin(), v1.end(), 10);
	if (ret)
		cout << "找到了" << endl;
	else
		cout << "没找到" << endl;

count

统计相同元素的个数

		vector<int> v1;
	for (size_t i = 0; i < 10; i++)
	{
		v1.push_back(i);
		v1.push_back(i + 1);
	}

	int num =count(v1.begin(), v1.end(), 9);
	cout << num<<endl;

count_if

按条件统计相同元素个数

class FindCondition
{
  bool operator()(int val)
  {
    return 10==val;
  }
};
		vector<int> v1;
	for (size_t i = 0; i < 10; i++)
	{
		v1.push_back(i);
		v1.push_back(i + 1);
	}
int num =count_if(v1.begin(), v1.end(), FindCondition());
	cout << num<<endl;