思路:
树形dp
注意0不存在逆元,任何一个数乘以0就变成0了,就没有价值浪,所以要暴力转移
代码:
#pragma GCC optimize(2)#pragma GCC optimize(3)#pragma GCC optimize(4)#includeusing namespace std;#define fi first#define se second#define pi acos(-1.0)#define LL long long//#define mp make_pair#define pb push_back#define ls rt<<1, l, m#define rs rt<<1|1, m+1, r#define ULL unsigned LL#define pll pair #define pli pair #define pii pair #define piii pair #define mem(a, b) memset(a, b, sizeof(a))#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);//headconst int N = 1e6 + 10;const int MOD = 1e9 + 7;struct edge { int to; int next;}edge[N*2];LL cnt[N], _cnt[N];int head[N], tot = 0;void add_edge(int u, int v) { edge[tot].to = v; edge[tot].next = head[u]; head[u] = tot++;}LL q_pow(LL n, LL k) { LL ans = 1; while(k) { if(k&1) ans = (ans * n) % MOD; n = (n * n) % MOD; k >>= 1; } return ans;}void dfs(int o, int u) { cnt[u] = 1; for (int i = head[u]; ~i; i = edge[i].next) { int v = edge[i].to; if(v != o) { dfs(u, v); cnt[u] = (cnt[u] * (cnt[v]+1)) % MOD; } }}void DFS(int o, int u) { for (int i = head[u]; ~i; i = edge[i].next) { int v = edge[i].to; if(v != o) { LL t = 1; if(cnt[v]+1 != MOD) t = (cnt[u] * q_pow(cnt[v]+1, MOD-2)) % MOD; else { for (int i = head[u]; ~i; i = edge[i].next) { int vv = edge[i].to; if(vv != o && vv != v) { t = (t * (cnt[vv]+1)) % MOD; } } } _cnt[v] = (_cnt[u]*t + 1) % MOD; DFS(u, v); } }}int main() { int n, u, v; scanf("%d", &n); for (int i = 1; i <= n; i++) head[i] = -1; for (int i = 1; i < n; i++) { scanf("%d %d", &u, &v); add_edge(u, v); add_edge(v, u); } dfs(1, 1); _cnt[1] = 1; DFS(1, 1); for (int i = 1; i <= n; i++) { printf("%lld\n", (cnt[i] * _cnt[i]) % MOD); } return 0;}