Linear Programming and 9-square fetch of Network Flow

Algorithm Implementation Question 8-9 getting the number of squares (Exercise 8-20)
? Problem description:
In a checker with M * n squares, each square has a positive integer. We need to take the number from the square
The square where the number 2 is located does not have a public edge, and the sum of the retrieved numbers is the largest. Design a number fetch algorithm that meets the requirements.
? Programming task:
For a given checker, program the number to find the maximum sum.
? Data input:
Input data is provided by the file input.txt. There are two positive integers m and n in the row 1st of the file, indicating the number of rows on the board respectively.
And the number of columns. In the next m row, each row has n positive integers, indicating the number in the checker square.
? Result output:
When the program ends, the maximum sum of the number is output to the output.txt file.
Input File example
Output file example
Input.txt
Output.txt
3 3
1 2 3
3 2 3
2 3 1
11

Question:

Maximum vertex weight independent set = total vertex weight-minimum vertex weight overwrite set = total vertex weight-minimum cut over ......

Code:

  1 const inf=maxlongint;  2 type node=record  3      from,go,next,v:longint;  4      end;  5 var  tot,i,j,n,m,maxflow,l,r,s,t,x,y,sum:longint;  6      h,head,q,cur:array[0..1000] of longint;  7      e:array[0..50000] of node;  8      num:array[0..50,0..50] of longint;  9      function min(x,y:longint):longint; 10       begin 11       if x<y then exit(x) else exit(y); 12       end; 13 procedure ins(x,y,z:longint); 14  begin 15  inc(tot); 16  e[tot].from:=x;e[tot].go:=y;e[tot].v:=z;e[tot].next:=head[x];head[x]:=tot; 17  end; 18 procedure insert(x,y,z:longint); 19  begin 20  if y>100000 then exit; 21  ins(x,y,z);ins(y,x,0); 22  end; 23 function bfs:boolean; 24  var i,x,y:longint; 25  begin 26  fillchar(h,sizeof(h),0); 27  l:=0;r:=1;q[1]:=s;h[s]:=1; 28  while l<r do 29   begin 30   inc(l); 31   x:=q[l]; 32   i:=head[x]; 33   while i<>0 do 34    begin 35    y:=e[i].go; 36    if (e[i].v<>0) and (h[y]=0) then 37     begin 38      h[y]:=h[x]+1; 39      inc(r);q[r]:=y; 40     end; 41    i:=e[i].next; 42    end; 43   end; 44  exit (h[t]<>0); 45  end; 46 function dfs(x,f:longint):longint; 47  var i,y,used,tmp:longint; 48  begin 49  if x=t then exit(f); 50  used:=0; 51  i:=cur[x]; 52  while i<>0 do 53   begin 54   y:=e[i].go; 55   if (h[y]=h[x]+1) and (e[i].v<>0) then 56    begin 57    tmp:=dfs(y,min(e[i].v,f-used)); 58    dec(e[i].v,tmp);if e[i].v<>0 then cur[x]:=i; 59    inc(e[i xor 1].v,tmp); 60    inc(used,tmp); 61    if used=f then exit(f); 62    end; 63   i:=e[i].next; 64   end; 65  if used=0 then h[x]:=-1; 66  exit(used); 67  end; 68 procedure dinic; 69  begin 70  while bfs do 71   begin 72   for i:=s to t do cur[i]:=head[i]; 73   inc(maxflow,dfs(s,inf)); 74   end; 75  end; 76 procedure init; 77  begin 78  tot:=1; 79  readln(n,m);sum:=0;s:=0;t:=n*m+1; 80  fillchar(num,sizeof(num),60); 81  for i:=1 to n do for j:=1 to m do num[i,j]:=(i-1)*m+j; 82  for i:=1 to n do 83   begin 84    for j:=1 to m do 85     begin 86      read(x);inc(sum,x); 87      if odd(i+j) then insert(s,num[i,j],x) else insert(num[i,j],t,x); 88     end; 89   readln; 90   end; 91  end; 92 procedure main; 93  begin 94  for i:=1 to n do 95   for j:=1 to m do 96    if odd(i+j) then 97     begin 98      insert(num[i,j],num[i,j+1],inf); 99      insert(num[i,j],num[i,j-1],inf);100      insert(num[i,j],num[i-1,j],inf);101      insert(num[i,j],num[i+1,j],inf);102     end;103  maxflow:=0;104  dinic;105  writeln(sum-maxflow);106  end;107 begin108  assign(input,‘grid.in‘);assign(output,‘grid.out‘);109  reset(input);rewrite(output);110  init;111  main;112  close(input);close(output);113 end.  

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