【树状数组】段改动，点查询

利用差分，先得到一个差分序列（如：（1,2,3,5)的差分序列为(1,1,1,2)）

当[i,j]段中全部数均加上数m时。在差分序列的i位置加上m,在j+1位置减去m就可以

求和利用树状数组

下面是pascal程序：

var
  a,fai:array[0..1000] of longint;
  c:char;
  n,i,x,y,f,m:longint;

function lowbit(x:longint):longint;
begin
  lowbit:=x and (-x);
end;

procedure modify(k,d:longint);
begin
  while k<=n do begin
    fai[k]:=fai[k]+d;
    k:=k+lowbit(k);
  end;
end;

function sum(x:longint):longint;
begin
  sum:=0;
  while x>0 do begin
    sum:=sum+fai[x];
    x:=x-lowbit(x);
  end;
end;

begin
  readln(n);
  for i:=1 to n do begin
    read(a[i]);
    modify(i,a[i]-a[i-1]);
  end;
  readln(m);
  for i:=1 to m do begin
    read(c);
    if c='C' then begin
      readln(x,y,f);
      modify(x,f);
      modify(y+1,-f);
    end;
    if c='Q' then begin
      readln(x);
      writeln(sum(x));
    end;
  end;
  readln;
end.