dbt

Procedure Relocate(s : state; b : base_index)
{ Move base for state s to a new place beginning at b }
begin
    foreach input character c for the state s
    { i.e. foreach c such that check[base[s] + c]] = s }
    begin
        check[b + c] := s;     { mark owner }
        base[b + c] := base[base[s] + c];     { copy data }
        { the node base[s] + c is to be moved to b + c;
          Hence, for any i for which check[i] = base[s] + c, update check[i] to b + c }
        foreach input character d for the node base[s] + c
        begin
            check[base[base[s] + c] + d] := b + c
        end;
        check[base[s] + c] := none     { free the cell }
    end;
    base[s] := b
end

Definition . For a transition from state s to t which takes character c as the input, the condition maintained in the double-array trie is:

check[base[s] + c] = s
base[s] + c = t

s

根据定义2，base[s] + c = t;

而 s, base[s], t, base[t], base[b+c] ,u，b 均为 数组下标,c,d为字符序列码，即偏移量。

base[s]只是一个基地址，与数组中该下标对应的base，check是否为空，无关。

base[s] = k

base[s] + c = t;  b + c = t',  base[b+c] = base[t'];  因此：

check[b + c] := s; { mark owner }

base[b + c] := base[base[s] + c]; { copy data }

可以理解为： check[t'] = s = check[t]; base[t'] = base[t]; 即将 t（base[s] + c） 结点的base，check 值复制到 t'结点中。

再调整t结点的孩子结点的check值，使其指向新的父节点t'。

check[i] = base[s] + c 即 check[i] = t; 

u = base[t] + d = base[base[s] + c] + d ; check[u] = check[base[base[s]+c] + d];

check[u] = t 即是：　　

check[base[base[s]+c] + d] = base[s] + c = t

修改父节点后：

check[base[base[s]+c] + d] = b+c = t'

释放原先的t结点

check[base[s] + c] := none 即是 check[t] := none

令s指向新的孩子结点：

base[s] = b;