打印杨辉三角形,行数小于20,每行第一个数顶格输出,数字之间有一个空格...答:var a:array[1..100,1..100] of longint;n,i,j:longint;begin read(n);a[1,1]:=1;for i:=2 to n do begin a[i,1]:=1;a[i,i]:=1;for j:=2 to i-1 do a[i,j]:=a[i-1,j-1]+a[i-1,j];end;for i:=1 to n do begin for j:=1 to i do write(a[i...