O(n log n)將結束時間或開始時間排序都可以，在另外一條序列中選擇上一場比賽和下一場比賽開始時間不沖突的比賽加入。var n:longint; a,b:array[1..2000000] of longint;PRocedure qsort(l,r:longint);var i,j,m,t:longint;begin i:=l;j:=r; m:=b[(l+r)div 2]; repeat while b[i]<m do inc(i); while b[j]>m do dec(j); if i<=j then begin t:=a[i];a[i]:=a[j];a[j]:=t; t:=b[i];b[i]:=b[j];b[j]:=t; inc(i);dec(j); end; until i>j; if i<r then qsort(i,r); if l<j then qsort(l,j);end;var i,ans,sum:longint;begin readln(n); for i:=1 to n do readln(a[i],b[i]); qsort(1,n); ans:=b[1]; for i:=2 to n do if a[i]>=ans then begin inc(sum); ans:=b[i]; end; writeln(sum+1);end.
