STL源碼剖析之算法：prev_permutation

template <class BidirectionIterator>
bool prev_permutation(BidirectionIterator first, BidirectionIterator last) {
    if(first == last) return false;
    BidirectionIterator i = first;
    ++i;
    if(i == last) return false;
    i = last;
    --i;

    for(;;) {
        BidirectionIterator ii = i;
        --i;

        if(*ii < *i) {
            BidirectionIterator j = last;
            while(!(*--j < *i));
            iter_swap(i, j);
            reverse(ii, last);
            return true;
        }

        if(i == first) {
            reverse(first, last);
            return false;
        }
    }
}