Topic link:
https://vjudge.net/problem/POJ-3349
Topic meaning:
Each snowflake has six branches, represented by six integers, which are traversed clockwise or counterclockwise starting from any branch. Enter multiple snowflakes to determine whether there are snowflakes with the same shape.
For example, if the input is 1 2 3 4 5 6,
Then 2 3 4 5 6 1, 3 4 5 6 1 2, ..., 6 5 4 3 2 1, 5 4 3 2 1 6, etc. are all the same shape.
Problem solving ideas:
The idea of the minimum representation is used here, and the input 6 numbers are pushed forward and backward in turn to find the minimum representation (which can be understood as the smallest lexicographical order), and then sort them to determine whether there are adjacent ones that are equal.
1 #include<iostream> 2 #include<algorithm> 3 #include<cstring> 4 #include<cstdio> 5 using namespace std; 6 const int maxn = 100000 + 10; 7 const int INF = 0x3f3f3f3f; 8 struct snow 9 { 10 int a[6]; 11 bool operator <(const snow& b)const 12 { 13 int i = 0; 14 while(a[i] == b.a[i] && i < 6)i++; 15 return i != 6 && a[i] < b.a[i]; 16 } 17 bool operator == (const snow& b)const 18 { 19 int i = 0; 20 while(a[i] == b.a[i] && i < 6)i++; 21 return i == 6; 22 } 23 snow(int b[]) 24 { 25 26 snow tmp; 27 memset(a, INF, sizeof(a)); 28 for(int start = 0; start < 6; start++) 29 { 30 for(int j = 0; j < 6; j++)//顺 31 tmp.a[j] = b[(start + j) % 6]; 32 if(tmp < *this)*this = tmp;//最小表示 33 34 for(int j = 0; j < 6; j++)//逆 35 tmp.a[j] = b[(start - j + 6) % 6]; 36 if(tmp < *this)*this = tmp;//最小表示 37 } 38 } 39 snow(){} 40 }s[maxn]; 41 int main() 42 { 43 int n, a[6]; 44 scanf("%d", &n); 45 for(int i = 0; i < n; i++) 46 { 47 for(int j = 0; j <6; j++) 48 scanf("%d", &a[j]); 49 s[i] = snow(a); 50 } 51 sort(s, s + n); 52 bool ok = 0; 53 for(int i = 0; i < n - 1; i++) 54 { 55 if(s[i] == s[i + 1]) 56 { 57 ok = 1; 58 break; 59 } 60 } 61 if(ok)cout<<"Twin snowflakes found."<<endl; 62 else cout<<"No two snowflakes are alike."<<endl; 63 return 0; 64 }