Question

我有一个具有结构

的多图

multimap< pair<int,int>, bool >

我已插入数据，看起来像这样

I is [0] Int is [5] Bool is [0]
I is [0] Int is [100] Bool is [0]
I is [0] Int is [100] Bool is [0]
I is [1] Int is [100] Bool is [0]
I is [1] Int is [100] Bool is [0]
I is [1] Int is [100] Bool is [0]
I is [2] Int is [5] Bool is [0]
I is [2] Int is [100] Bool is [0]
I is [2] Int is [100] Bool is [0]

我需要能够让地图的迭代器跳转到下一个我，而不会迭代其他我。

例如，我只想添加不具有相同 I 值的 Ints 。所以它可以去

添加5 + 100 + 5

因为这些是第一个具有不同我的值。我怎么能这样做呢？

Answer 1

嗯 - 您可以使用地图lower_bound功能 - 您需要将其应用于“下一个”主键 - 请参阅：

auto next_key(int key_first)
{
    return std::make_pair(key_first + 1, std::numeric_limits<int>::min());
}

因此，下一个要搜索的密钥对是(first + 1, INT_MIN)。

所以，循环：

for (auto i = data.begin(); 
          i != data.end(); 
          i = data.lower_bound(next_key(i->first.first)))
{
    std::cout << i->first.second << std::endl;
}

对于这些数据：

std::multimap< std::pair<int,int>, bool > data = {
    {{0,5},false},
    {{0,100},false},
    {{0,100},false},
    {{1,100},false},
    {{1,100},false},
    {{1,100},false},
    {{2,5},false},
    {{2,100},false},
    {{2,100},false}
};

你得到：

5
100
5

使用一对键搜索多图

1 个答案: