Question

为解决spoj问题编写的我的c ++代码没有被编译。它在我的电脑上编译非常weint但在spoj或ideone.com上编译。我无法理解它显示的错误。请帮助!! http://ideone.com/3Wce5t

  #include<iostream>
  #include<cstdio> 
  #include<algorithm>
  #include<vector>

   using namespace std;

    struct point{
    int xx;int yy;int zz;

    bool const operator < (point& b)
    const {
    return xx < b.xx;
    }
    };

    bool myfun(const point& a,const point& b)
    {
    return a.yy < b.yy;
    }





    const int N = 1000001;
    int tree[N],L[N],R[N];
    int next;
    vector <point> v;


    void build(int ID,int l,int r)
    {
    tree[ID] = 0;
    int m = (l+r)>>1;

    if(l<r)
    {
    L[ID] = next++;
    build(L[ID],l,m);
    R[ID] = next++;
    build(R[ID],m+1,r);
    }
    else
        {L[ID] = -1;R[ID] = -1;}
    }

    void update(int ID,int id,int l,int r,int loc)  //new ID and old id
    {
    int m = (l+r)>>1;

    if(l==r)
        {
        tree[ID] = 1;
        return; 
        }

    L[ID] = L[id];
    R[ID] = R[id];

    if(l<=loc && loc<=m)
        {L[ID] = next++;
        update(L[ID],L[id],l,m,loc);
        }
    if((m+1)<=loc && loc<=r)
        {R[ID] = next++;
        update(R[ID],R[id],m+1,r,loc);  
        }
    tree[ID] = tree[L[ID]] + tree[R[ID]];

    }

    int get(int id,int ID,int k,int l,int r)
    {
    if(l==r) return v[l].xx;

    int mid = (l+r)>>1;

    //cout<<tree[L[ID]] - tree[L[id]]<<' '<<k<<' '<<l<<' '<<r<<endl;

    if(tree[L[ID]]-tree[L[id]] >= k) 
            return get(L[id],L[ID],k,l,mid);
    else    
            return get(R[id],R[ID],k-(tree[L[ID]]-tree[L[id]]),mid+1,r);
    }


    int main()
    {
    int n,i,j,m;

    cin>>n>>m;

    v.resize(n);

    for(i=0;i<n;i++)
        {cin>>v[i].xx;
        v[i].yy = i;    
        }   

    sort(v.begin(),v.end());

    for(i=0;i<n;i++)
        v[i].zz = i;

    sort(v.begin(),v.end(),myfun);

    next = 2;

    build(1,0,n-1);

    vector <int> ind(n+1);
    ind[0] = 1;

    for(i=1;i<=n;i++)
        {
        ind[i] = next++;    
        update(ind[i],ind[i-1],0,n-1,v[i-1].zz);
            //ID and then location
        }//we set original v[i]'s position in sorted as 1

    int a,b,c;

    sort(v.begin(),v.end());

    for(i=0;i<m;i++)
        {
        cin>>a>>b>>c;
        a--;
        cout<<get(ind[a],ind[b],c,0,n-1)<<endl; 
        }

    }

我得到的错误是::

/usr/include/c++/4.3/bits/stl_algo.h: In function 'const _Tp& std::__median(const _Tp&, const _Tp&, const _Tp&) [with _Tp = point]':
        /usr/include/c++/4.3/bits/stl_algo.h:1919:   instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<point*, std::vector<point, std::aintocator<point> > >, _Size = int]'
        /usr/include/c++/4.3/bits/stl_algo.h:4783:   instantiated from 'void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<point*, std::vector<point, std::aintocator<point> > >]'
        prog.cpp:105:   instantiated from here
        /usr/include/c++/4.3/bits/stl_algo.h:93: error: no match for 'operator<' in '__a < __b'
        prog.cpp:20: note: candidates are: const bool point::operator<(point&) const
        /usr/include/c++/4.3/bits/stl_algo.h:94: error: no match for 'operator<' in '__b < __c'
        prog.cpp:20: note: candidates are: const bool point::operator<(point&) const
        /usr/include/c++/4.3/bits/stl_algo.h:96: error: no match for 'operator<' in '__a < __c'
        prog.cpp:20: note: candidates are: const bool point::operator<(point&) const
        /usr/include/c++/4.3/bits/stl_algo.h:100: error: no match for 'operator<' in '__a < __c'
        prog.cpp:20: note: candidates are: const bool point::operator<(point&) const
        /usr/include/c++/4.3/bits/stl_algo.h:102: error: no match for 'operator<' in '__b < __c'
        prog.cpp:20: note: candidates are: const bool point::operator<(point&) const

Answer 1

如错误中所述，编译器无法找到正确的比较运算符，因为它应该被定义为

bool const operator < (point b)

而不是

bool const operator < (point& b)

编辑：正如评注中所述，

bool const operator < ( point const & b)

可能是更好的方式

Answer 2

在struct：

之外移动重载运算符

struct point
{
    int xx;
    int yy;
    int zz;
};

bool const operator < (const point &a, const point &b) const
{
    return xx < b.xx;
}

C ++代码没有编译

2 个答案: