poj 2763 Housewife Wind(树链剖分)
2014-10-17 09:33
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题目链接:poj 2763 Housewife Wind
题目大意:给定一棵树,然后2种操作:
0 u:输出路径s到u的权值和,并且s变成u
1 i w:节点i增加w
解题思路:树链剖分,然后用线段树维护,单点修改区间查询。
题目大意:给定一棵树,然后2种操作:
0 u:输出路径s到u的权值和,并且s变成u
1 i w:节点i增加w
解题思路:树链剖分,然后用线段树维护,单点修改区间查询。
#include <cstdio> #include <cstring> #include <algorithm> using namespace std; const int maxn = 100005; int N, Q, S, ne; int first[maxn], jump[maxn * 2]; int id, far[maxn], son[maxn], cnt[maxn], dep[maxn], top[maxn], idx[maxn]; struct Edge { int u, v, w; void set (int u, int v, int w) { this->u = u; this->v = v; this->w = w; } }ed[maxn * 2]; void dfs_fir (int u, int pre, int d) { far[u] = pre; dep[u] = d; cnt[u] = 1; son[u] = 0; for (int i = first[u]; i + 1; i = jump[i]) { int v = ed[i].v; if (v == pre) continue; dfs_fir(v, u, d+1); cnt[u] += cnt[v]; if (cnt[son[u]] < cnt[v]) son[u] = v; } } void dfs_sec(int u, int rot) { top[u] = rot; idx[u] = id++; if (son[u]) dfs_sec(son[u], rot); for (int i = first[u]; i + 1; i = jump[i]) { int v = ed[i].v; if (v == far[u] || v == son[u]) continue; dfs_sec(v, v); } } inline void add_Edge(int u, int v, int w) { ed[ne].set(u, v, w); jump[ne] = first[u]; first[u] = ne++; } #define lson(x) ((x)<<1) #define rson(x) (((x)<<1)|1) typedef long long ll; int lc[maxn << 2], rc[maxn << 2]; ll s[maxn << 2]; inline void pushup(int u) { s[u] = s[lson(u)] + s[rson(u)]; } void build (int u, int l, int r) { lc[u] = l; rc[u] = r; s[u] = 0; if (l == r) return; int mid = (l + r) / 2; build(lson(u), l, mid); build(rson(u), mid + 1, r); pushup(u); } void modify (int u, int x, int w) { if (lc[u] == x && rc[u] == x) { s[u] = w; return; } int mid = (lc[u] + rc[u]) / 2; if (x <= mid) modify(lson(u), x, w); else modify(rson(u), x, w); pushup(u); } ll query(int u, int l, int r) { if (l <= lc[u] && rc[u] <= r) return s[u]; ll ret = 0; int mid = (lc[u] + rc[u]) / 2; if (l <= mid) ret += query(lson(u), l, r); if (r > mid) ret += query(rson(u), l, r); return ret; } void init () { ne = 0; id = 1; int u, v, w; memset(first, -1, sizeof(first)); for (int i = 0; i < N - 1; i++) { scanf("%d%d%d", &u, &v, &w); add_Edge(u, v, w); add_Edge(v, u, w); } dfs_fir(1, 0, 0); dfs_sec(1, 1); build(1, 1, N); for (int i = 0; i < N - 1; i++) { if (dep[ed[i*2].u] < dep[ed[i*2].v]) swap(ed[i*2].u, ed[i*2].v); modify(1, idx[ed[i*2].u], ed[i*2].w); } } ll solve (int u, int v) { ll ret = 0; int p = top[u], q = top[v]; while (p != q) { if (dep[p] < dep[q]) { swap(p, q); swap(u, v); } ret += query(1, idx[p], idx[u]); u = far[p]; p = top[u]; } if (u == v) return ret; if (dep[u] > dep[v]) swap(u, v); ret += query(1, idx[son[u]], idx[v]); return ret; } int main () { while (scanf("%d%d%d", &N, &Q, &S) == 3) { init(); int k, u, w; while (Q--) { scanf("%d%d", &k, &u); if (k) { scanf("%d", &w); modify(1, idx[ed[u*2 - 2].u], w); } else { printf("%lld\n", solve(S, u)); S = u; } } } return 0; }
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