2102: [Usaco2010 Dec]The Trough Game
Time Limit: 10 Sec Memory Limit: 64 MB
Submit: 117 Solved: 84
[Submit][Status]
Description
Farmer John and Bessie are playing games again. This one has to do with troughs of water. Farmer John has hidden N (1 <= N <= 20) troughs behind the barn, and has filled some of them with food. Bessie has asked M (1 <= M <= 100) questions of the form, "How many troughs from this list (which she recites) are filled?". Bessie needs your help to deduce which troughs are actually filled. Consider an example with four troughs where Bessie has asked these questions (and received the indicated answers): 1) "How many of these troughs are filled: trough 1" --> 1 trough is filled 2) "How many of these troughs are filled: troughs 2 and 3" --> 1 trough is filled 3) "How many of these troughs are filled: troughs 1 and 4" --> 1 trough is filled 4) "How many of these troughs are filled: troughs 3 and 4" --> 1 trough is filled From question 1, we know trough 1 is filled. From question 3, we then know trough 4 is empty. From question 4, we then know that trough 3 is filled. From question 2, we then know that trough 2 is empty. 求N位二进制数X，使得给定的M个数，满足X and Bi=Ci ,Bi ci分别是读入的两个数
Input
* Line 1: Two space-separated integers: N and M * Lines 2..M+1: A subset of troughs, specified as a sequence of contiguous N 0‘s and 1‘s, followed by a single integer that is the number of troughs in the specified subset that are filled.
Output
* Line 1: A single line with: * The string "IMPOSSIBLE" if there is no possible set of filled troughs compatible with Farmer John‘s answers. * The string "NOT UNIQUE" if Bessie cannot determine from the given data exactly what troughs are filled. * Otherwise, a sequence of contiguous N 0‘s and 1‘s specifying which troughs are filled.
Sample Input
4 4
1000 1
0110 1
1001 1
0011 1
Sample Output
1010
HINT
Source
题解：一上来居然没有别的想法——只有暴力。。。然后写了个纯粹的二进制穷举，然后，然后，然后，居然AC了？！？！44ms也是醉大了= =
1 type 2 point=^node; 3 node=record 4 g:longint; 5 next:point; 6 end; 7 var 8 i,j,k,l,m,n,t:longint; 9 a:array[0..10000] of point; 10 b,c,d:array[0..10000] of longint; 11 c1,c2:char; 12 procedure add(x,y:longint);inline; 13 var p:point; 14 begin 15 new(p);p^.g:=y; 16 p^.next:=a[x];a[x]:=p; 17 end; 18 procedure dfs(x:longint);inline; 19 var i,j,k,l:longint;p:point; 20 begin 21 if x>n then 22 begin 23 for i:=1 to m do if b[i]>0 then exit; 24 if t=0 then 25 begin 26 for i:=1 to n do d[i]:=c[i]; 27 t:=1; 28 end 29 else 30 begin 31 writeln(‘NOT UNIQUE‘); 32 halt; 33 end; 34 end 35 else 36 begin 37 p:=a[x];l:=0; 38 while p<>nil do 39 begin 40 if b[p^.g]=0 then 41 begin 42 l:=1; 43 break; 44 end; 45 p:=p^.next; 46 end; 47 if l=0 then 48 begin 49 p:=a[x]; 50 while p<>nil do 51 begin 52 dec(b[p^.g]); 53 p:=p^.next; 54 end; 55 c[x]:=1; 56 dfs(x+1); 57 p:=a[x]; 58 while p<>nil do 59 begin 60 inc(b[p^.g]); 61 p:=p^.next; 62 end; 63 end; 64 c[x]:=0; 65 dfs(x+1); 66 end; 67 end; 68 69 begin 70 readln(n,m); 71 for i:=1 to m do a[i]:=nil; 72 for i:=1 to m do 73 begin 74 for j:=1 to n do 75 begin 76 read(c1); 77 if c1=‘1‘ then add(j,i); 78 end; 79 readln(b[i]); 80 end; 81 t:=0; 82 dfs(1); 83 IF t=0 then write(‘IMPOSSIBLE‘) else for i:=1 to n do write(d[i]); 84 writeln; 85 readln; 86 end.