基础算法（二）——队列

const
dx:array[1..4]of longint=(0,-1,0,1);
dy:array[1..4]of longint=(1,0,-1,0);
var
n,m,i,j,tj:longint;
a:array[-10..100,-10..100]of boolean;
x:char;
state:array[0..4000,0..4000]of longint;

procedure bfs(x,y:longint);
var
head,tail,i:longint;
begin
    inc(tj);
    a[x,y]:=false;
    head:=0;tail:=1;
    state[1,1]:=x;state[1,2]:=y;
    repeat
         inc(head);
         for i:=1 to 4 do
         begin
             x:=state[head,1]+dx[i];
             y:=state[head,2]+dy[i];
             if (x>0)and(x<=m)and(y>0)and(y<=n)and(a[x,y]=true) then
             begin
                 inc(tail);
                 state[tail,1]:=x;
                 state[tail,2]:=y;
                 a[x,y]:=false;
             end;
         end;
    until head>=tail;
end;

begin
    readln(m,n);
    fillchar(a,sizeof(a),true);
    for i:=1 to m do
    begin
        for j:=1 to n do
        begin
            read(x);
            if x=‘0‘ then a[i,j]:=false;
        end;
        readln;
    end;
    for i:=1 to m do
    for j:=1 to n do
    if a[i,j]=true then bfs(i,j);
    write(tj);
end.

// （该程序由网上搜集，要用到BFS，找到一个细胞后就进行BFS操作即可）