hdu 5977 Garden of Eden(点分治+状压dp)
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题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=5977
题解:这题一看就知道是状压dp然后看了一下很像是点分治(有点明显)然后就是简单的点分治+状压dp,这里只要稍微改一下模版就行了。还有注意一下这里的cau状态枚举然后就没什么了
#include <iostream> #include <cstring> #include <cstdio> using namespace std; typedef long long ll; const int M = 5e4 + 10; struct Edge { int v , next; }edge[M << 1]; int head[M] , e , Size , root , n , k , a[M] , ssr; ll ans; bool vis[M]; void init() { memset(head , -1 , sizeof(head)); memset(vis , false , sizeof(vis)); ans = 0; e = 0; ssr = ((1 << k) - 1); } void add(int u , int v) { edge[e].v = v; edge[e].next = head[u]; head[u] = e++; } int size[M] , mx[M]; ll Hash[1025]; void dfs_size(int u , int pre) { size[u] = 1; mx[u] = 0; for(int i = head[u] ; i != -1 ; i = edge[i].next) { int v = edge[i].v; if(v == pre || vis[v]) continue; dfs_size(v , u); size[u] += size[v]; mx[u] = max(mx[u] , size[v]); } } void dfs_root(int r , int u , int pre) { mx[u] = max(mx[u] , size[r] - size[u]); if(mx[u] < Size) Size = mx[u] , root = u; for(int i = head[u] ; i != -1 ; i = edge[i].next) { int v = edge[i].v; if(v == pre || vis[v]) continue; dfs_root(r , v , u); } } void get_root(int u , int pre) { dfs_size(u , pre); dfs_root(u , u , pre); } int num , State[M]; void find_state(int u , int pre , int state) { State[num++] = state; for(int i = head[u] ; i != -1 ; i = edge[i].next) { int v = edge[i].v; if(vis[v] || v == pre) continue; find_state(v , u , state | (1 << a[v])); } } ll cau(int u , int state) { num = 0; find_state(u , -1 , state); memset(Hash , 0 , sizeof(Hash)); ll sum = 0; for(int i = 0 ; i < num ; i++) Hash[State[i]]++; for(int i = 0 ; i < num ; i++) { Hash[State[i]]--; sum += Hash[ssr];//这里由于是枚举时0枚举不到所以先加上ssr^0. for (int s0 = State[i]; s0; s0 = (s0 - 1) & State[i]) sum += Hash[((1 << k) - 1) ^ s0]; Hash[State[i]]++; } return sum; } void dfs(int u) { Size = n; get_root(u , -1); ans += cau(root , (1 << a[root])); vis[root] = true; int rt = root; for(int i = head[root] ; ~i ; i = edge[i].next) { int v = edge[i].v; if(vis[v]) continue; ans -= cau(v , (1 << a[rt]) | (1 << a[v])); dfs(v); } } int main() { while(scanf("%d%d" , &n , &k) != EOF) { init(); for(int i = 1 ; i <= n ; i++) scanf("%d" , &a[i]) , a[i]--; for(int i = 0 ; i < n - 1 ; i++) { int u , v; scanf("%d%d" , &u , &v); add(u , v); add(v , u); } if (k == 1) { printf("%lld\n", (ll)n * (ll)n); continue; } dfs(1); printf("%lld\n" , ans); } return 0; }
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