foo.cc: In function 'int DP()':
foo.cc:33:3: error: reference to 'prev' is ambiguous
   prev[1][i][0]=1;
   ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:34:3: error: reference to 'prev' is ambiguous
   prev[1][i][1]=i-1;
   ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:40:3: error: reference to 'prev' is ambiguous
   prev[i][1][0]=i-1;
   ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:41:3: error: reference to 'prev' is ambiguous
   prev[i][1][1]=1;
   ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:49:5: error: reference to 'prev' is ambiguous
     prev[i][j][0]=i-1;
     ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:50:5: error: reference to 'prev' is ambiguous
     prev[i][j][1]=j;
     ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:53:5: error: reference to 'prev' is ambiguous
     prev[i][j][0]=i;
     ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:54:5: error: reference to 'prev' is ambiguous
     prev[i][j][1]=j-1;
     ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:63:10: error: reference to 'prev' is ambiguous
   int tx=prev[x][y][0];
          ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc:64:10: error: reference to 'prev' is ambiguous
   int ty=prev[x][y][1];
          ^~~~
foo.cc:19:5: note: candidates are: int prev [25][25][2]
 int prev[N][N][2];//记录节点前驱
     ^~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:66:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/c++/7/bits/stl_iterator_base_funcs.h:220:5: note:                 template<class _BidirectionalIterator> _BidirectionalIterator std::prev(_BidirectionalIterator, typename std::iterator_traits<_Iter>::difference_type)
     prev(_BidirectionalIterator __x, typename
     ^~~~
foo.cc: In function 'int main()':
foo.cc:70:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:73:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&num[i][j]);
    ~~~~~^~~~~~~~~~~~~~~~~

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