BZOJ 3331 [BeiJing2013]压力-Tarjan + 树上差分

Solution

Tarjan 点双缩点， 加上树上差分计算。

注意特判。。。 我特判挂了好久呜呜呜

Code

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<vector>
 #define rd read()
 using namespace std;

 const int N = 1e5 + ;
 const int M = 2e5 + ;
 const int base = ;

 int head[N], tot;
 int Head[N << ], Tot;
 int low[N], dfn[N], cnt, col, c[N], cut[N], n, m, Q;
 int f[N << ][], nd, id[N], idf[N << ], dep[N << ];
 int st[N], tp, num[N], sum[N << ];

 vector<int> q[N << ];

 struct edge {
     int nxt, to;
 }e[M << ], E[M << ];

 int read() {
     int X = , p = ; char c = getchar();
     for (; c > '' || c < ''; c = getchar()) if (c == '-') p = -;
     for (; c >= '' && c <= ''; c = getchar()) X = X *  + c - '';
     return X * p;
 }

 void add(int u, int v) {
     e[++tot].to = v;
     e[tot].nxt = head[u];
     head[u] = tot;
 }

 void Add(int u, int v) {
     E[++Tot].to = v;
     E[Tot].nxt = Head[u];
     Head[u] = Tot;
 }

 void tarjan(int u) {
     low[u] = dfn[u] = ++cnt;
     st[++tp] = u;
     int flag = ;
     for (int i = head[u]; i; i = e[i].nxt) {
         int nt = e[i].to;
         if (!dfn[nt]) {
             tarjan(nt);
             low[u] = min(low[u], low[nt]);
             if (low[nt] >= dfn[u]) {
                 flag++;
                 if (flag >  || u - )
                     cut[u] = ;
                 col++;
                 for (; tp;) {
                     int v = st[tp--];
                     q[col].push_back(v);
                     if (v == nt)
                         break;
                 }
                 q[col].push_back(u);
             }
         }
         else low[u] = min(low[u], dfn[nt]);
     }
 }

 void dfs(int u) {
     for (int i = Head[u]; i; i = E[i].nxt) {
         int nt = E[i].to;
         if (f[u][] == nt)
             continue;
         f[nt][] = u;
         dep[nt] = dep[u] + ;
         dfs(nt);
     }
 }

 int LCA(int x, int y) {
     if (dep[x] < dep[y])
         swap(x, y);
     for (int k = base - ; ~k; --k)
         if (dep[f[x][k]] >= dep[y])
             x = f[x][k];
     if (x == y)
         return x;
     for (int k = base - ; ~k; --k)
         if (f[x][k] != f[y][k])
             x = f[x][k], y = f[y][k];
     return f[x][];
 }

 void dfs2(int u) {
     for (int i = Head[u]; i; i = E[i].nxt) {
         int nt = E[i].to;
         if (nt == f[u][])
             continue;
         dfs2(nt);
         sum[u] += sum[nt];
     }
     if(u > col)
         num[idf[u]] += sum[u];
 }

 int main()
 {
     //freopen("1.in","r", stdin);
     //freopen("out.out","w",stdout);
     n = rd; m = rd; Q = rd;
     for (int i = ; i <= m; ++i) {
         int u = rd, v = rd;
         add(u, v); add(v, u);
     }
     tarjan();
     nd = col;
     for (int i = ; i <= n; ++i)
         if (cut[i]) c[i] = ++nd, idf[nd] = i;
     for (int i = ; i <= col; ++i)
         for(int j = , len = q[i].size(); j < len; ++j) {
             int x = q[i][j];
             if (cut[x])
                 Add(i, c[x]), Add(c[x], i);
             else c[x] = i;
         }
     dep[] = ;
     dfs();
     for (int k = ; k < base; ++k)
         for (int i = ; i <= nd; ++i)
             f[i][k] = f[f[i][k - ]][k - ];
     for (; Q; Q--) {
         int u = rd, v = rd, lca;
         if (c[u] <= col) num[u]++;
         if (c[v] <= col) num[v]++;
         u = c[u]; v = c[v];
         if (u == v) continue;
         lca = LCA(u, v);
         sum[v]++; sum[u]++;
         sum[lca]--; sum[f[lca][]]--;
     }
     dfs2();
     for (int i = ; i <= n; ++i)
         printf("%d\n", num[i]);
 }