查找一个地图是否是另一个地图的子集 [英] Find if one map is subset of another

问题描述

我有两个STL映射 std :: map< int，int> foo = {{1,0}，{2,0}，{3,0}，{4,0}，{5,0}，{6,0}}; 和 std :: map< int，int> bar = {{2,0}，{4,0}，{5，0}};

I have two STL maps std::map<int, int> foo = {{1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}}; and std::map<int, int> bar = {{2, 0}, {4, 0}, {5, 0}};

是foo的子集。

由于元素在map中排序，我认为
从foo中的bar中找到第一个元素，然后找到连续的元素
从foo中的那个位置。

Since the elements are sorted in map, I would think to find the first element from bar in foo, and then find consecutive elements from bar in foo from that location.

这里的问题是我不能找出一个办法做到这一点STL地图在cpp 。
我可以将地图中搜索范围从地图中的某个位置减少到地图结尾吗？

The problem here is I'm not able to figure out a way to do that with STL maps in cpp. Can I reduce the search range in map for every find from a location in map to the end of the map?

我希望我解释了这个问题。 / p>

I hope I explained the problem.

推荐答案

使用 std :: includes 算法与自定义比较器仅比较键：

Use std::includes algorithm with a custom comparator that compares only the keys:

#include <map>
#include <algorithm>
#include <iostream>

int main()
{
    std::map<int, int> foo = {{1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}};
    std::map<int, int> bar = {{2, 0}, {4, 0}, {5, 0}};
    typedef std::pair<int,int> pair;

    std::cout <<
       std::includes(foo.begin(), foo.end(), bar.begin(), bar.end(),
           [](const pair& p1, const pair& p2)
           {
               return p1.first < p2.first;
           });
}

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