POJ 3177

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原文链接：http://www.cnblogs.com/wmzisfoolish/archive/2012/04/06/2435189.html

POJ 3177

题目大意：同poj 3352。

解：同poj3352，但记得处理重边的问题。

View Code

  1 //poj 3177
  2 const
  3         maxn=5111;
  4         maxm=11111;
  5 type
  6         data=record
  7           dest, next, op: longint;
  8         end;
  9 var
 10         edge: array[1..maxm*2]of data;
 11         pre, dfn, low, deg, vect: array[1..maxn]of longint;
 12         g: array[1..maxn, 1..maxn]of boolean;
 13         visit:array[1..maxn]of boolean;
 14         n, m, time, tot, ans: longint;
 15 procedure add(x, y: longint);
 16 begin
 17   inc(tot);
 18   with edge[tot] do begin
 19     dest := y;
 20     next := vect[x];
 21     vect[x] := tot;
 22     op := tot + 1;
 23   end;
 24   inc(tot);
 25   with edge[tot] do begin
 26     dest := x;
 27     next := vect[y];
 28     vect[y] := tot;
 29     op := tot - 1;
 30   end;
 31 end;
 32 
 33 procedure init;
 34 var
 35         i, x, y: longint;
 36 begin
 37   tot := 0; ans := 0;
 38   fillchar(vect, sizeof(vect), 0);
 39   fillchar(g, sizeof(g), 0);
 40   readln(n, m);
 41   for i := 1 to m do begin
 42     readln(x, y);
 43     if not g[x, y] then begin
 44       add(x, y);
 45       g[x, y] := true;
 46       g[y, x] := true;
 47     end;
 48   end;
 49 end;
 50 
 51 procedure tarjan(x: longint);
 52 var
 53         i: longint;
 54 begin
 55   inc(time);
 56   dfn[x] := time; low[x] := time;
 57   visit[x] := true;
 58   i := vect[x];
 59   while i<>0 do
 60     with edge[i] do begin
 61      if (pre[x]<>dest) then
 62       if (dfn[dest]=0) then begin
 63         pre[dest] := x;
 64         tarjan(dest);
 65         pre[dest] := 0;
 66         if (low[dest]<low[x]) then low[x] := low[dest];
 67       end
 68         else if visit[dest] then begin
 69           if (dfn[dest]<low[x]) then low[x] := dfn[dest];
 70         end;
 71       i := next;
 72     end;
 73   visit[x] := false;
 74 end;
 75 
 76 procedure main;
 77 var
 78         i, u: longint;
 79 begin
 80   fillchar(dfn, sizeof(dfn), 0);
 81   fillchar(pre, sizeof(pre), 0);
 82   fillchar(visit, sizeof(visit), 0);
 83   time := 0;
 84   for i := 1 to n do if dfn[i]=0 then tarjan(i);
 85   fillchar(deg, sizeof(deg), 0);
 86   for u := 1 to n do begin
 87     i := vect[u];
 88     while i<>0 do
 89       with edge[i] do begin
 90         if (low[u]<>low[dest]) then begin
 91           inc(deg[low[u]]);
 92           inc(deg[low[dest]]);
 93         end;
 94         i := next;
 95       end;
 96   end;
 97   for i := 1 to time do
 98     if deg[i] >> 1 = 1 then inc(ans);
 99   if ans = 1 then ans := 0;
100   ans := (ans + 1) >> 1;
101 end;
102 
103 procedure print;
104 begin
105   writeln(ans);
106 end;
107 
108 begin
109   assign(input,'1.txt'); reset(input);
110   while not seekeof do begin
111   init;
112   main;
113   print;
114   end;
115 end.

转载于:https://www.cnblogs.com/wmzisfoolish/archive/2012/04/06/2435189.html