usaco-1.3-wormhole

这个属于DFS枚举：

/*
ID: qq104801
LANG: C++
TASK: wormhole
QQ:104804687
*/

#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>
#include <cmath>

using namespace std;

#define loop(i,n) for(int i=0;i<(n);i++)
#define loop2(i,n) for(int i=1;i<=(n);i++)
const int maxn=13;
const int inf=1<<30;

int n,x[maxn],y[maxn];
int partner[maxn],next_on_right[maxn];

bool cycle_exists(void)
{
  /*
  for(int i=1;i<=n;i++)
    cout<<i<<":"<<partner[i]<<" ";
  cout<<endl;
  */

  for(int start=1;start<=n;start++)
  {
    int pos=start;
    for(int count=0;count<n;count++)
      pos=next_on_right[partner[pos]];
    if(pos!=0) return true;
  }
  return false;
}

int solve(void)
{
  int i,total=0;
  for(i=1;i<=n;i++)
    if(partner[i]==0)break;

  if(i>n)
  {
    if(cycle_exists())
      return 1;
    else
      return 0;
  }

  for(int j=i+1;j<=n;j++)
    if(partner[j]==0)
    {
      partner[i]=j;
      partner[j]=i;      
      total+=solve();
      partner[i]=partner[j]=0;
    }
  return total;
}

void test()
{   
  freopen("wormhole.in","r",stdin);  
  freopen("wormhole.out","w",stdout); 
  cin>>n;
  loop2(i,n)
  {
    cin>>x[i]>>y[i];
    //cout<<x[i]<<":"<<y[i]<<endl;
  }

  loop2(i,n)
    loop2(j,n)
      if(x[j]>x[i]&&y[i]==y[j])
        if(next_on_right[i]==0 || x[j]-x[i]<x[next_on_right[i]]-x[i])
          next_on_right[i]=j;

  cout<<solve()<<endl;
}

int main () 
{        
    test();        
    return 0;
}

test data:

USACO Training
Grader Results     
4 users online
CHN/2 IND/1 KAZ/1

USER: cn tom [qq104801]
TASK: wormhole
LANG: C++

Compiling...
Compile: OK

Executing...
   Test 1: TEST OK [0.008 secs, 3380 KB]
   Test 2: TEST OK [0.008 secs, 3380 KB]
   Test 3: TEST OK [0.005 secs, 3380 KB]
   Test 4: TEST OK [0.011 secs, 3380 KB]
   Test 5: TEST OK [0.008 secs, 3380 KB]
   Test 6: TEST OK [0.011 secs, 3380 KB]
   Test 7: TEST OK [0.011 secs, 3380 KB]
   Test 8: TEST OK [0.014 secs, 3380 KB]
   Test 9: TEST OK [0.016 secs, 3380 KB]
   Test 10: TEST OK [0.019 secs, 3380 KB]

All tests OK.

Your program ('wormhole') produced all correct answers! This is your submission #2 for this problem. Congratulations!

Here are the test data inputs:

------- test 1 [length 18 bytes] ----
4
0 0
1 0
1 1
0 1
------- test 2 [length 23 bytes] ----
4
21 7
11 23
11 7
5 10
------- test 3 [length 37 bytes] ----
6
1 15
20 15
17 11
22 21
25 11
20 17
------- test 4 [length 117 bytes] ----
6
879221060 76350727
161945371 76350727
380619073 76350727
896289713 76350727
852891025 852349940
519959866 76350727
------- test 5 [length 159 bytes] ----
8
491007315 324539677
99582962 578796531
491007315 768974420
373902710 578796531
99582962 332416760
946724340 321414549
976998120 638226676
49126574 437845706
------- test 6 [length 198 bytes] ----
10
987878530 332490544
545074228 332490544
571194544 278963943
32922985 229703843
571194544 851333603
90862786 28227282
219975775 267376202
219975775 332490544
90862786 62367085
872930617 951881113
------- test 7 [length 243 bytes] ----
12
636437309 704270751
695056713 700147825
636437309 356396548
921201220 589666013
430411607 671693685
324259336 671693685
723442153 589666013
528904109 419799944
921201220 356396548
723442153 856537355
691516566 726853849
941903572 634527403
------- test 8 [length 53 bytes] ----
12
0 0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
10 1
10 0
------- test 9 [length 243 bytes] ----
12
572085931 667578536
964406504 667578536
656852339 870264627
110654368 823223484
513786208 528178006
620147001 528178006
227047539 667578536
656852339 528178006
945298921 528178006
945298921 870264627
840030425 870264627
828839382 528178006
------- test 10 [length 236 bytes] ----
12
5138254 91583927
607865472 167507876
51248250 8250417
675467597 611809280
157130071 946061365
138261433 967068106
769112165 966993974
675467597 144175980
769112165 475105594
51248250 144175980
947874168 111530133
164921238 967068106