题目链接：http://codeforces.com/gym/100735/problem/D
题意：给你几根木棒，每根木棒的长度已知，问最多能组成几组三角形，每根木棒只能用一次
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdlib> 5 #include <cstdio> 6 #include <vector> 7 #include <ctime> 8 #include <queue> 9 #include <list> 10 #include <set> 11 #include <map> 12 using namespace std; 13 #define INF 0x3f3f3f3f 14 typedef long long LL; 15 16 int dp[10][1<<16], a[20], p[4]; 17 int main() 18 { 19 int n; 20 while(~scanf("%d", &n)) 21 { 22 for(int i = 1; i <= n; i++) 23 scanf("%d", &a[i]); 24 memset(dp, 0, sizeof(dp)); 25 for(int i = 1; i <= n/3; i++)//最多n/3组三角形 26 { 27 for(int j = 0; j < (1<<n); j++) 28 { 29 int te = j, k = 0; 30 while(te) 31 { 32 k += te % 2; 33 te >>= 1; 34 } 35 if(k != (i-1)*3) 36 continue; 37 for(int l1 = 0; l1 < n; l1++)//每次选三根木棒出来 38 { 39 int t1 = j; 40 if(t1 & (1<<l1)) 41 continue; 42 for(int l2 = 0; l2 < n; l2++) 43 { 44 int t2 = t1 | (1<<l1); 45 if(t2 & (1<<l2)) 46 continue; 47 for(int l3 = 0; l3 < n; l3++) 48 { 49 int t3 = t2 | (1<<l2); 50 if(t3 & (1<<l3)) 51 continue; 52 int t4 = t3 | (1<<l3); 53 p[0] = a[l1+1], p[1] = a[l2+1], p[2] = a[l3+1]; 54 sort(p, p+3); 55 if(p[0]+p[1]>p[2]) 56 dp[i][t4] = max(dp[i][t4], dp[i-1][j]+1); 57 else 58 dp[i][t4] = max(dp[i][t4], dp[i-1][j]); 59 } 60 } 61 } 62 } 63 } 64 int res = 0;//注意结果不是dp[n/3][1<<n] 65 for(int i = 0; i < (1<<n); i++) 66 { 67 int te = i, k = 0; 68 while(te) 69 { 70 k += te % 2; 71 te >>= 1; 72 } 73 if(k == (n/3)*3) 74 res = max(res, dp[n/3][i]); 75 } 76 printf("%d ", res); 77 } 78 return 0; 79 }