1562: [NOI2009]变换序列 - BZOJ

Description

Input

Output

Sample
Input

5

1 1 2 2 1

Sample Output

1 2 4 0 3

HINT

30%的数据中N≤50；
60%的数据中N≤500；
100%的数据中N≤10000。

二分图匹配，倒着匹配，每次选小的增广（随便乱yy一下，应该就可以证明是字典序最小的吧）

 1 const

 2     maxn=10010;

 3 var

 4     first,link:array[0..maxn]of longint;

 5     a:array[0..maxn,0..1]of longint;

 6     next,last:array[0..maxn]of longint;

 7     n:longint;

 8

 9 procedure swap(var x,y:longint);

10 var

11     t:longint;

12 begin

13     t:=x;x:=y;y:=t;

14 end;

15

16 procedure init;

17 var

18     i,x:longint;

19 begin

20     read(n);

21     for i:=1 to n do

22       begin

23         read(x);

24         a[i,0]:=i+x;

25         a[i,1]:=i-x;

26         if a[i,0]>n then dec(a[i,0],n);

27         if a[i,1]<1 then inc(a[i,1],n);

28         if a[i,0]>a[i,1] then swap(a[i,0],a[i,1]);

29       end;

30 end;

31

32 var

33     time:longint;

34     flag:array[0..maxn]of longint;

35

36 function path(x:longint):boolean;

37 var

38     i:longint;

39 begin

40     for i:=0 to 1 do

41       if (i=0) or (a[x,i]<>a[x,i-1]) then

42         if flag[a[x,i]]<>time then

43         begin

44           flag[a[x,i]]:=time;

45           if (link[a[x,i]]=0) or (path(link[a[x,i]])) then

46           begin

47             link[a[x,i]]:=x;

48             exit(true);

49           end;

50         end;

51     exit(false);

52 end;

53

54 procedure work;

55 var

56     i:longint;

57 begin

58     for i:=n downto 1 do

59       begin

60         inc(time);

61         if path(i)=false then

62         begin

63           writeln(‘No Answer‘);

64           exit;

65         end;

66       end;

67     for i:=1 to n do

68       if link[a[i,0]]=i then write(a[i,0]-1,‘ ‘)

69       else write(a[i,1]-1,‘ ‘);

70 end;

71

72 begin

73     init;

74     work;

75 end.