bzoj 1061 志愿者招募 费用流

详见BYV的博客，写的非常全面https://www.byvoid.com/blog/noi-2008-employee

/**************************************************************
    Problem:
    User: BLADEVIL
    Language: Pascal
    Result: Accepted
    Time: ms
    Memory: kb
****************************************************************/
 
//By BLADEVIL
var
    n, m                        :longint;
    pre, other, len, cost       :array[..] of longint;
    last                        :array[..] of longint;
    l                           :longint;
    source, sink                :longint;
    ans                         :longint;
    flag                        :array[..] of boolean;
    dis, que, father            :array[..] of longint;
     
function min(a,b:longint):longint;
begin
    if a>b then min:=b else min:=a;
end;
     
procedure connect(a,b,c,d:longint);
begin  
    inc(l);
    pre[l]:=last[a];
    last[a]:=l;
    other[l]:=b;
    len[l]:=c;
    cost[l]:=d;
end;
     
procedure init;
var
    i                           :longint;
    x, y, z                     :longint;
     
begin
    read(n,m);
    source:=n+; sink:=source+;
    x:=;
    l:=;
    for i:= to n do
    begin
        read(y);
        if y-x> then
        begin
            connect(source,i,y-x,);
            connect(i,source,,);
        end else
        begin
            connect(i,sink,x-y,);
            connect(sink,i,,);
        end;
        x:=y;
    end;
    connect(n+,sink,x,);
    connect(sink,n+,,);
    for i:= to m do
    begin
        read(x,y,z);
        connect(x,y+,maxlongint div ,z);
        connect(y+,x,,-z);
    end;
    for i:= to n+ do
    begin
        connect(i,i-,maxlongint div ,);
        connect(i-,i,,);
    end;
end;
 
function spfa:boolean;
var
    h, t, cur                   :longint;
    q, p                        :longint;
begin
    filldword(dis,sizeof(dis) div ,maxlongint div );
    que[]:=source;
    dis[source]:=;
    h:=; t:=;
    while t<>h do
    begin
        h:=h mod +;
        cur:=que[h];
        flag[cur]:=false;
        q:=last[cur];
        while q<> do
        begin
            p:=other[q];
            if len[q]> then
                if dis[p]>dis[cur]+cost[q] then
                begin
                    father[p]:=q;
                    dis[p]:=dis[cur]+cost[q];
                    if not flag[p] then
                    begin
                        t:=t mod +;
                        que[t]:=p;
                        flag[p]:=true;
                    end;
                end;
            q:=pre[q];
        end;
    end;
    if dis[sink]=maxlongint div  then exit(false) else exit(true);
end;
 
procedure update;
var
    low, cur                    :longint;
begin
    cur:=sink;
    low:=maxlongint;
    while cur<>source do
    begin
        low:=min(low,len[father[cur]]);
        cur:=other[father[cur] xor ];
    end;
    cur:=sink;
    while cur<>source do
    begin
        dec(len[father[cur]],low);
        inc(len[father[cur] xor ],low);
        ans:=ans+low*cost[father[cur]];
        cur:=other[father[cur] xor ];
    end;
end;
 
procedure main;
begin
    while spfa do
        update;
    writeln(ans);
end;
 
begin
    init;
    main;
end.