C++标准库全排列算法

下面是gnu c++的源码

template<typename _BidirectionalIterator, typename _Compare>
bool
__next_permutation(_BidirectionalIterator __first,
	_BidirectionalIterator __last, _Compare __comp) {
	if (__first == __last)
		return false;
	_BidirectionalIterator __i = __first;
	++__i;
	if (__i == __last)
		return false;
	__i = __last;
	--__i;

	for (;;) {
		_BidirectionalIterator __ii = __i;
		--__i;
		if (__comp(__i, __ii)) {
			_BidirectionalIterator __j = __last;
			while (!__comp(__i, --__j)) {
			}
			std::iter_swap(__i, __j);
			std::__reverse(__ii, __last,
				std::__iterator_category(__first));
			return true;
		}
		if (__i == __first) {
			std::__reverse(__first, __last,
				std::__iterator_category(__first));
			return false;
		}
	}
}

过程比较简单，下面是示意图