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Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 262144/262144 K (Java/Others)
Total Submission(s): 597 Accepted Submission(s): 274
解题思路:状态压缩。用dp[i][j]表示选择i状态所表示的数时,以第j个数为结尾时的最大和。转移方程: dp[i|(1<<k)][k] = max(dp[i|(1<<k)][k], dp[i][j] + a[i]*a[j])。
#include<stdio.h> #include<algorithm> #include<string.h> #include<math.h> #include<string> #include<iostream> #include<queue> #include<stack> #include<map> #include<vector> #include<set> using namespace std; typedef long long LL; #define mid (L+R)/2 #define lson rt*2,L,mid #define rson rt*2+1,mid+1,R #pragma comment(linker, "/STACK:102400000,102400000") const int maxn = 1e5+300; const LL INF = 1000000000000; typedef long long LL; typedef unsigned long long ULL; int a[30], p[30]; int choice[maxn]; LL dp[maxn][30]; int cal(int x){ int ret = 0; while(x){ if(x&1) ret++; x = x>>1; } return ret; } int main(){ int T, n, cas = 0; scanf("%d",&T); //预处理出来数字i二进制中有多少个1,因为在有定位置的数时,需要保证前面有那么多个1 for(int i = 0; i <= (1<<16); i++){ choice[i] = cal(i); } while(T--){ scanf("%d",&n); for(int i = 0; i < n; i++){ scanf("%d%d",&a[i],&p[i]); } for(int i = 0; i <= (1<<n); i++){ for(int j = 0; j <= n; j++){ dp[i][j] = -INF; } } a[n] = 0; //只是为了初始化 dp[0][n] = 0; //只是为了初始化 for(int i = 0; i < (1<<n); i++){ for(int j = 0; j <= n; j++){ if(dp[i][j]!= -INF){ for(int k = 0; k < n; k++){ if((i&(1<<k)) == 0&&(p[k] == -1 || p[k] == choice[i])){ dp[i|(1<<k)][k] = max(dp[i|(1<<k)][k],dp[i][j] + a[j]*a[k]); } } } } } LL ans = -INF; for(int i = 0; i < n; i++){ ans = max(ans, dp[(1<<n)-1][i]); } printf("Case #%d:\n",++cas); printf("%lld\n",ans); } return 0; }
HDU 5691 ——Sitting in Line——————【状压动规】
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原文地址:http://www.cnblogs.com/chengsheng/p/5524362.html