Light OJ 1348 - Aladdin and the Return Journey(树链剖分)

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题目链接：Light OJ 1348 - Aladdin and the Return Journey

题目大意：给定一棵树，两种操作

0 i j：ij路径上的权值和
1 i v：将第i个节点的权值修改为v

解题思路：树链剖分的裸题。

#include <cstdio>
#include <cstring>
#include <algorithm>using namespace std;const int maxn = 30005;int N, Q, ne, first[maxn], jump[maxn * 2], link[maxn * 2], val[maxn];
int id, idx[maxn], dep[maxn], far[maxn], son[maxn], top[maxn], cnt[maxn];void dfs (int u, int pre, int d) {far[u] = pre;dep[u] = d;son[u] = 0;cnt[u] = 1;for (int i = first[u]; i + 1; i = jump[i]) {int v = link[i];if (v == pre)continue;dfs(v, u, d + 1);cnt[u] += cnt[v];if (cnt[son[u]] < cnt[v])son[u] = v;}
}void dfs(int u, int rot) {top[u] = rot;idx[u] = ++id;if (son[u])dfs(son[u], rot);for (int i = first[u]; i + 1; i = jump[i]) {int v = link[i];if (v == far[u] || v == son[u])continue;dfs(v, v);}
}inline void add_Edge(int u, int v) {link[ne] = v;jump[ne] = first[u];first[u] = ne++;
}#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)
int lc[maxn << 2], rc[maxn << 2], 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);
}int query(int u, int l, int r) {if (l <= lc[u] && rc[u] <= r)return s[u];int mid = (lc[u] + rc[u]) / 2, ret = 0;if (l <= mid)ret += query(lson(u), l, r);if (r > mid)ret += query(rson(u), l, r);pushup(u);return ret;
}void modify(int u, int x, int v) {if (x == lc[u] && x == rc[u]) {s[u] = v;return;}int mid = (lc[u] + rc[u]) / 2;if (x <= mid)modify(lson(u), x, v);elsemodify(rson(u), x, v);pushup(u);
}void init () {scanf("%d", &N);for (int i = 1; i <= N; i++)scanf("%d", &val[i]);int u, v;ne = id = 0;memset(first, -1, sizeof(first));for (int i = 1; i < N; i++) {scanf("%d%d", &u, &v);u++, v++;add_Edge(u, v);add_Edge(v, u);}dfs(1, 0, 0);dfs(1, 1);build(1, 1, N);for (int i = 1; i <= N; i++)modify(1, idx[i], val[i]);
}int query (int u, int v) {int p = top[u], q = top[v], ret = 0;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 (dep[u] > dep[v])swap(u, v);ret += query(1, idx[u], idx[v]);return ret;
}int main () {int cas;scanf("%d", &cas);for (int kcas = 1; kcas <= cas; kcas++) {init();scanf("%d", &Q);printf("Case %d:\n", kcas);int k, u, v;while (Q--) {scanf("%d%d%d", &k, &u, &v);if (k)modify(1, idx[u+1], v);elseprintf("%d\n", query(u+1, v+1));}}return 0;
}