翻转单词

#include <iostream>
#include <cstring>
using namespace std;
void *reversem (void * pointer,const size_t mem_n);
void *reverse_adjacent_m(void * pointer,const size_t head_size,const size_t total_size);
void *reverse_non_adjacent_m(void * pointer,const size_t head_size,const size_t end_size,const size_t total_size);

int main(void)
{
    char str[50001];
    cin.getline(str,50001);
    int head=0,end=0;
    int N=strlen(str);

    for(int j=0;j<N;j++)
    {
        if(str[j]==' '&&str[j-1]!=' ')
        {
            head=j-1;
        }
        if(str[j]==' '&&str[j+1]!=' ')
        {
            end=j+1;
        }

        if(str[head+1]==' '&&str[end-1]==' ')
        {
            reverse_non_adjacent_m(str,head+1,N-end,N);
            //cout<<N<<' '<<head<<' '<<end<<endl;

            N=N-end;
            head=end=0;
            j=-1;
        }

    }
    for (size_t i=0;i<strlen(str);i++)
    cout<<str[i];
    cout<<endl;
    return 0;
}

void *reversem (void * pointer,const size_t mem_n)
{
    if(pointer==NULL) return pointer;
    if(mem_n<2) return pointer;
    char *beg=static_cast<char*>(pointer);
    char *end=beg+mem_n-1;
    char tmp;
    for(;beg<end;beg++,end--)
    {
        tmp=*beg;
        *beg=*end;
        *end=tmp;
    }
    return pointer;
}
void *reverse_adjacent_m(void * pointer,const size_t head_size,const size_t total_size)
{
    if(pointer==NULL) return pointer;
    if(total_size<2) return pointer;
    char *beg=static_cast<char*>(pointer);
    char *mid=beg+head_size;
    reversem(beg,head_size);
    //char *end=beg+total_size-1;
    reversem(mid,total_size-head_size);
    reversem(beg,total_size);
    return pointer;
}

void *reverse_non_adjacent_m(void * pointer,const size_t head_size,const size_t end_size,const size_t total_size)
{
    if(pointer==NULL) return pointer;
    if(total_size<3) return pointer;
    if(head_size>=total_size||end_size>=total_size) return pointer;
    if(total_size<(head_size+end_size)) return pointer;
    char *beg=static_cast <char*> (pointer);
    reversem(beg,head_size);
    reversem(beg+total_size-end_size,end_size);
    reversem(beg,total_size);
    return pointer;
}