如何知道一个key是map中的第几大值?

[BlueSky2008]

我用
map.find(key)-map.begin()但好像类型不能匹配。应该怎么做？

[boxban]

int n = std::distance( map.begin(), map.find(key));

[BlueSky2008]

嗯，多谢。找到了：
The template function sets a count n to zero. It then effectively advances first and increments n until first == last. If InIt is a random-access iterator type, the function evaluates the expression n += last - first. Otherwise, it performs each iterator increment by evaluating ++first.
看来效率也不怎么样啊。