readln全WA read 就对了

AC程序

var
a:array[1..100001]of longint;
n,k,i,j:longint;

procedure sort(l,r: longint);
var
i,j,x,y: longint;
begin
i:=l;
j:=r;
x:=a[(l+r) div 2];
repeat
while a[i]<x do
inc(i);
while x<a[j] do
dec(j);
if not(i>j) then
begin
y:=a[i];
a[i]:=a[j];
a[j]:=y;
inc(i);
j:=j-1;
end;
until i>j;
if l<j then
sort(l,j);
if i<r then
sort(i,r);
end;

begin
read(n,k);
for i:=1 to n do read(a[i]);
sort(1,n);j:=0;
writeln(a[n-k+1]);
end.

WA程序

var
a:array[1..100001]of longint;
n,k,i,j:longint;

procedure sort(l,r: longint);
var
i,j,x,y: longint;
begin
i:=l;
j:=r;
x:=a[(l+r) div 2];
repeat
while a[i]<x do
inc(i);
while x<a[j] do
dec(j);
if not(i>j) then
begin
y:=a[i];
a[i]:=a[j];
a[j]:=y;
inc(i);
j:=j-1;
end;
until i>j;
if l<j then
sort(l,j);
if i<r then
sort(i,r);
end;

begin
readln(n,k);
for i:=1 to n do readln(a[i]);
sort(1,n);j:=0;
writeln(a[n-k+1]);
end.