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HDU 3001 Travelling 状压DP

2024-07-17 03:35:24   234人阅读

三进制状压。调了一整天，一开始用记忆化搜索一直超时，后来改成了递推，代码能力真是弱。。

后来瓜神提供了一个思路，如果建立一个超级源点然后用记忆化搜索的话，应该可以过。。。。

#include <cstdio>#include <cstring>#include <iostream>#include <map>#include <set>#include <vector>#include <string>#include <queue>#include <deque>#include <bitset>#include <list>#include <cstdlib>#include <climits>#include <cmath>#include <ctime>#include <algorithm>#include <stack>#include <sstream>#include <numeric>#include <fstream>#include <functional>using namespace std;#define MP make_pair#define PB push_backtypedef long long LL;typedef unsigned long long ULL;typedef vector<int> VI;typedef pair<int,int> pii;const int INF = INT_MAX / 2;const double eps = 1e-8;const LL LINF = 1e17;const double DINF = 1e60;const int maxn = 12;const int maxs = 59049;const int p3[maxn] = {1,3,9,27,81,243,729,2187,6561,19683,59049};int n,m,dist[maxn][maxn];int f[maxn][maxs + maxn];int st[maxs + maxn][maxn];bool sok[maxs + maxn][maxn];inline void expand(int st,int *arr) {    int pos = 0;    while(st) {        arr[pos++] = st % 3; st /= 3;    }}inline bool ok(int s,int t) {    for(int i = 0;i < t;i++)         if(st[s][i] == 0) return false;    return true;}int main() {    for(int i = 0;i <= maxs;i++) expand(i,st[i]);    for(int i = 0;i <= maxs;i++) {        for(int j = 0;j <= 10;j++) sok[i][j] = ok(i,j);    }    while(~scanf("%d%d",&n,&m)) {        memset(dist,-1,sizeof(dist));        for(int i = 0;i < m;i++) {            int u,v,w; scanf("%d%d%d",&u,&v,&w); u--; v--;            dist[u][v] = dist[v][u] = (                dist[u][v] == -1 ? w : min(dist[u][v],w));        }        for(int i = 0;i < n;i++)             for(int j = 0;j < p3[n];j++)                f[i][j] = INF;        int ans = INF;        for(int i = 0;i < n;i++) f[i][p3[i]] = 0;        for(int j = 0;j < p3[n];j++) {            for(int i = 0;i < n;i++) if(f[i][j] < INF)  {                for(int k = 0;k < n;k++) if(dist[k][i] != -1 && st[j][k] < 2) {                    f[k][j + p3[k]] = min(f[k][j + p3[k]],f[i][j] + dist[k][i]);                }            }        }        for(int i = 0;i < n;i++) {            for(int j = 0;j < p3[n];j++) {                if(sok[j][n]) {                    ans = min(ans,f[i][j]);                }            }        }        if(ans >= INF) puts("-1");        else printf("%d\n",ans);    }    return 0;}

　　


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