如何在排序的 C++ 向量中找到一个值？
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How to find a value in a sorted C++ vector?
提问by user2813274
I have looked at findand binary_search, but find doesn't take advantage of the fact that the vector is sorted, and binary_search only returns a true or false, not where it found the value. Is there any function that can give me the best of both worlds?
我看过find和binary_search，但 find 没有利用向量已排序的事实，并且 binary_search 只返回 true 或 false，而不是在它找到值的地方。有什么功能可以让我两全其美？
回答by Steve Howard
std::lower_boundwill do that for you. It's in the equivalent-behavior section at the top for binary_search.
std::lower_bound将为您做到这一点。它位于 binary_search 顶部的等效行为部分。
回答by paxdiablo
There is a method, std::equal_range, which will give you a pair containing the lower and upper bound of the subset holding the desired value. If both of those items in the pair are identical, then the value you were looking for doesn't exist.
有一种方法，std::equal_range，它将为您提供一对，其中包含保存所需值的子集的下限和上限。如果这对中的这两个项目相同，则您要查找的值不存在。
回答by Gabriel Schreiber
template<class T, class U>
bool contains(const std::vector<T>& container, const U& v)
{
auto it = std::lower_bound(
container.begin(),
container.end(),
v,
[](const T& l, const U& r){ return l < r; });
return it != container.end() && *it == v;
}
