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