【SDOI 2011】染色

【题目链接】

点击打开链接

【算法】

树链剖分

【代码】

本题，笔者求最近公共祖先并没有用树链剖分“往上跳”的方式，而是用倍增法。笔者认为这样比较好写，代码可读性

比较高

此外，笔者的线段树并没有用懒惰标记，只要当前访问节点的线段总数为1，那么就下传

#include<bits/stdc++.h>
using namespace std;
#define MAXLOG 18
const int MAXN = 1e5 + ;
 
int i,n,m,timer,x,y,c,t;
int dep[MAXN],fa[MAXN],size[MAXN],son[MAXN],
        dfn[MAXN],top[MAXN],val[MAXN],pos[MAXN],anc[MAXN][MAXLOG];
vector<int> e[MAXN];
char opt[];
 
struct SegmentTree {
        struct Node {
                int l,r,sum,lcover,rcover;
        } Tree[MAXN*];
        inline void push_up(int index) {
                Tree[index].lcover = Tree[index<<].lcover;
                Tree[index].rcover = Tree[index<<|].rcover;
                Tree[index].sum = Tree[index<<].sum + Tree[index<<|].sum;
                if (Tree[index<<].rcover == Tree[index<<|].lcover) Tree[index].sum--;
        }
        inline void push_down(int index) {
                Tree[index<<].sum = Tree[index<<|].sum = ;
                Tree[index<<].lcover = Tree[index<<].rcover = Tree[index].lcover;
                Tree[index<<|].lcover = Tree[index<<|].rcover = Tree[index].rcover;
        }
        inline void build(int index,int l,int r) {
                int mid;
                Tree[index].l = l;
                Tree[index].r = r;
                if (l == r) {
                        Tree[index].lcover = Tree[index].rcover = val[pos[l]];
                        Tree[index].sum = ;
                        return;
                }
                mid = (l + r) >> ;
                build(index<<,l,mid);
                build(index<<|,mid+,r);
                push_up(index);
        }
        inline void modify(int index,int l,int r,int val) {
                int mid;
                if (Tree[index].l == l && Tree[index].r == r) {
                        Tree[index].lcover = Tree[index].rcover = val;
                        Tree[index].sum = ;
                        return;
                }
                if (Tree[index].sum == ) push_down(index);
                mid = (Tree[index].l + Tree[index].r) >> ;
                if (mid >= r) modify(index<<,l,r,val);
                else if (mid +  <= l) modify(index<<|,l,r,val);
                else {
                        modify(index<<,l,mid,val);
                        modify(index<<|,mid+,r,val);
                }
                push_up(index);
        }
        inline int query(int index,int l,int r) {
                int mid,t;
                if (Tree[index].l == l && Tree[index].r == r) return Tree[index].sum;
                if (Tree[index].sum == ) push_down(index);
                mid = (Tree[index].l + Tree[index].r) >> ;
                if (mid >= r) return query(index<<,l,r);
                else if (mid +  <= l) return query(index<<|,l,r);
                else {
                        t = ;
                        if (Tree[index<<].rcover == Tree[index<<|].lcover) t = ;
                        return query(index<<,l,mid) + query(index<<|,mid+,r) - t;
                }
        }
        inline int get(int index,int pos) {
                int mid;
                if (Tree[index].l == Tree[index].r) return Tree[index].lcover;
                if (Tree[index].sum == ) push_down(index);
                mid = (Tree[index].l + Tree[index].r) >> ;
                if (mid >= pos) return get(index<<,pos);
                else return get(index<<|,pos);
        }
} T;
inline void dfs1(int x) {
        int i,y;
        anc[x][] = fa[x];
        for (i = ; i < MAXLOG; i++) {
                if (dep[x] < ( << i)) break;
                anc[x][i] = anc[anc[x][i-]][i-];
        }
        size[x] = ;
        for (i = ; i < e[x].size(); i++) {
                y = e[x][i];
                if (fa[x] != y) {
                        dep[y] = dep[x] + ;
                        fa[y] = x;
                        dfs1(y);
                        size[x] += size[y];
                        if (size[y] > size[son[x]]) son[x] = y;
                }
        }
}
inline void dfs2(int x,int tp) {
        int i,y;
        dfn[x] = ++timer;
        pos[timer] = x;
        top[x] = tp;
        if (son[x]) dfs2(son[x],tp);
        for (i = ; i < e[x].size(); i++) {
                y = e[x][i];
                if (fa[x] != y && son[x] != y)
                        dfs2(y,y);
        }
}
inline int lca(int x,int y) {
        int i,t;
        if (dep[x] > dep[y]) swap(x,y);
        t = dep[y] - dep[x];
        for (i = ; i <= MAXLOG - ; i++) {
                if (t & ( << i))
                    y = anc[y][i];
        }
        if (x == y) return x;
        for (i = MAXLOG - ; i >= ; i--) {
                if (anc[x][i] != anc[y][i]) {
                        x = anc[x][i];
                        y = anc[y][i];
                }
        }
        return anc[x][];
}
inline void modify(int x,int y,int c) {
        int tx = top[x],
            ty = top[y];
        while (tx != ty) {
                T.modify(,dfn[tx],dfn[x],c);
                x = fa[tx]; tx = top[x];
        }
        T.modify(,dfn[y],dfn[x],c);
}
inline int query(int x,int y) {
        int tx = top[x],
            ty = top[y],ans = ;
        while (tx != ty) {
                ans += T.query(,dfn[tx],dfn[x]);
                if (T.get(,dfn[tx]) == T.get(,dfn[fa[tx]])) ans--;
                x = fa[tx]; tx = top[x];
        }
        ans += T.query(,dfn[y],dfn[x]);
        return ans;
}
 
int main() {
 
        scanf("%d%d",&n,&m);
        for (i = ; i <= n; i++) scanf("%d",&val[i]);
        for (i = ; i < n; i++) {
                scanf("%d%d",&x,&y);
                e[x].push_back(y);
                e[y].push_back(x);
        }
 
        dfs1();
        dfs2(,);
        T.build(,,timer);
 
        while (m--) {
                scanf("%s",opt);
                if (opt[] == 'C') {
                        scanf("%d%d%d",&x,&y,&c);
                        t = lca(x,y);
                        modify(x,t,c); modify(y,t,c);
                } else {
                        scanf("%d%d",&x,&y);
                        t = lca(x,y);
                        printf("%d\n",query(x,t)+query(y,t)-);
                }
        }
 
    return ;
}