【BZOJ1103】[POI2007]大都市meg【树链剖分】【线段树】【或 树状数组 + dfs序】

【题目链接】

想都没想直接树剖去了...看了题解发现树状数组维护dfs序也可以做。

树剖：

/* Pigonometry */#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 250005;int n, head[maxn], cnt;struct _edge {int v, next;} g[maxn];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline void add(int u, int v) {g[cnt] = (_edge){v, head[u]};head[u] = cnt++;}int pre[maxn], son[maxn], size[maxn], dfn[maxn], clo, top[maxn];int tr[maxn << 2];inline void dfs(int x) {size[x] = 1; son[x] = 0;for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x]) {pre[g[i].v] = x;dfs(g[i].v);size[x] += size[g[i].v];if(size[g[i].v] > size[son[x]]) son[x] = g[i].v;}}inline void dfs2(int x, int tp) {top[x] = tp; dfn[x] = ++clo;if(son[x]) dfs2(son[x], tp);for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x] && g[i].v ^ son[x])dfs2(g[i].v, g[i].v);}inline void pushup(int p) {tr[p] = tr[p << 1] + tr[p << 1 | 1];}inline void build(int p, int l, int r) {if(l == r) {if(l == 1) tr[p] = 0;else tr[p] = 1;return;}int mid = l + r >> 1;build(p << 1, l, mid); build(p << 1 | 1, mid + 1, r);pushup(p);}inline int query(int p, int l, int r, int x, int y) {if(x <= l && r <= y) return tr[p];int mid = l + r >> 1, res = 0;if(x <= mid) res += query(p << 1, l, mid, x, y);if(y > mid) res += query(p << 1 | 1, mid + 1, r, x, y);return res;}inline int querychain(int u) {int res = 0;for(; u; u = pre[top[u]])res += query(1, 1, clo, dfn[top[u]], dfn[u]);return res;}inline void change(int p, int l, int r, int x, int c) {if(l == r && r == x) {tr[p] = c;return;}int mid = l + r >> 1;if(x <= mid) change(p << 1, l, mid, x, c);else change(p << 1 | 1, mid + 1, r, x, c);pushup(p);}int main() {n = iread();for(int i = 1; i <= n; i++) head[i] = -1; cnt = 0;for(int i = 1; i < n; i++) {int u = iread(), v = iread();if(u > v) swap(u, v);add(u, v);}dfs(1); dfs2(1, 1);build(1, 1, clo);for(int T = iread(); T; ) {char ch = getchar(); for(; ch != 'W' && ch != 'A'; ch = getchar());if(ch == 'W') {T--;int u = iread();printf("%d\n", querychain(u));}else if(ch == 'A') {int u = iread(), v = iread();if(u > v) swap(u, v);change(1, 1, clo, dfn[v], 0);}}return 0;}

树状数组 + dfs序：

比树剖快2s...

/* Pigonometry */#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 250005, maxm = maxn << 1;int n, m, head[maxn], cnt, st[maxn], ed[maxn], clo, pre[maxn], tr[maxm];struct _edge {int v, next;} g[maxn];inline int iread() {int f = 1, x = 0; char ch = getchar();for(; ch < '0' || ch > '9'; ch = getchar()) f = ch == '-' ? -1 : 1;for(; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';return f * x;}inline void addedge(int u, int v) {g[cnt] = (_edge){v, head[u]};head[u] = cnt++;}inline void add(int x, int c) {for(; x <= m; x += x & -x) tr[x] += c;}inline int sum(int x) {int res = 0;for(; x; x -= x & -x) res += tr[x];return res;}inline void dfs(int x) {st[x] = ++clo;add(clo, 1);for(int i = head[x]; ~i; i = g[i].next) if(g[i].v ^ pre[x]) {pre[g[i].v] = x;dfs(g[i].v);}ed[x] = ++clo;add(clo, -1);}int main() {n = iread(); m = n << 1;for(int i = 1; i <= n; i++) head[i] = -1; cnt = 0;for(int i = 1; i < n; i++) {int u = iread(), v = iread();if(u > v) swap(u, v);addedge(u, v);}dfs(1);for(int T = iread(); T; ) {char ch = getchar(); for(; ch != 'W' && ch != 'A'; ch = getchar());if(ch == 'W') {T--;int u = iread();printf("%d\n", sum(st[u]) - 1);}else if(ch == 'A') {int u = iread(), v = iread();if(u > v) swap(u, v);add(st[v], -1); add(ed[v], 1);}}return 0;}