luogu P2486 [SDOI2011]染色

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这道题第一眼看过去

显然嘛

树剖

搞呗

线段树挨个统计颜色段数

但是搞的时候需要记录一下线段树每个节点的左右子节点的颜色

因为如果左边子树的右儿子颜色和右边子树左儿子颜色一样ans要--

同时剖出来的链也要判断一下与上一次剖到的链的颜色是否相同

代码挺长的

写完debug整的我眼睛疼死

#include<cstdio>
#include<algorithm>
#define sev en
using namespace std;
#define N 100010

int n,m;
struct EDGE {
    int to,nxt;
} e[N << 1];
int head[N],cnt;
int a[N];

void add(int x,int y) {
    e[++cnt].to = y;
    e[cnt].nxt = head[x];
    //   e[cnt].w = z;
    head[x] = cnt;
}

int dep[N],fa[N],siz[N],heavy[N];

void dfs1(int x,int f,int d) {
    fa[x] = f;
    dep[x] = d;
    siz[x] = 1;
    for(int i = head[x]; i; i = e[i].nxt) {
        int v = e[i].to;
        if(v == fa[x])
            continue;
        dfs1(v,x,d + 1);
        siz[x] += siz[v];
        if(siz[v] > siz[heavy[x]])
        heavy[x] = v;
    }
    return ;
}

int dfn[N],top[N];

void dfs2(int u,int t) {
    dfn[u] = ++cnt;
    top[u] = t;
    a[cnt] = u;
    if(!heavy[u])
        return ;
    dfs2(heavy[u],t);
    for(int i = head[u]; i; i = e[i].nxt) {
        int v = e[i].to;
        if(v == fa[u] || v == heavy[u])
            continue;
        dfs2(v,v);
    }
    return ;
}

int sum[N << 2],left[N << 2],right[N << 2];

void pushup(int now) {
    sum[now] = sum[now << 1] + sum[now << 1 | 1];
    left[now] = left[now << 1];
    right[now] = right[now << 1 | 1];
    if(left[now << 1 | 1] == right[now << 1])
        sum[now]--;
    return ;
}

int col[N];

void build(int now,int l,int r) {
    if(l == r) {
        sum[now] = 1;
        left[now] = right[now] = col[a[l]];
        return ;
    }
    int mid = (l + r) >> 1;
    build(now << 1,l,mid);
    build(now << 1 | 1,mid + 1,r);
    pushup(now);
    return ;
}

int lazy[N << 2];

void pushdown(int now,int l,int r) {
    sum[now << 1] = sum[now << 1 | 1] = 1;
    left[now << 1] = right[now << 1] = left[now << 1 | 1] = right[now << 1 | 1] = lazy[now << 1] = lazy[now << 1 | 1] = lazy[now];
    lazy[now] = 0;
    return ;
}

void modify(int now,int l,int r,int x,int y,int c) {
    if(l == x && r == y) {
        sum[now] = 1;
        lazy[now] = left[now] = right[now] = c;
        return ;
    }
    if(lazy[now])
        pushdown(now,l,r);
    int mid = (l + r) >> 1;
    if(x > mid)
        modify(now << 1 | 1,mid + 1,r,x,y,c);
    else if(y <= mid)
        modify(now << 1,l,mid,x,y,c);
    else {
        modify(now << 1,l,mid,x,mid,c);
        modify(now << 1 | 1,mid + 1,r,mid + 1,y,c);
    }
    pushup(now);
    return ;
}

void get_modify(int x,int y,int c) {
    while(top[x] != top[y]) {
        if(dep[top[x]] > dep[top[y]])
            swap(x,y);
        modify(1,1,n,dfn[top[y]],dfn[y],c);
        y = fa[top[y]];
    }
    if(dep[x] > dep[y])
        swap(x,y);
    modify(1,1,n,dfn[x],dfn[y],c);
    return ;
}

int query(int now,int l,int r,int x,int y) {
    if(l == x && r == y)
        return sum[now];
    if(lazy[now])
        pushdown(now,l,r);
    int mid = (l + r) >> 1;
    if(x > mid)
    return query(now << 1 | 1,mid + 1,r,x,y);
    else if(y <= mid)
    return query(now << 1,l,mid,x,y);
    else{
    int ans = query(now << 1,l,mid,x,mid) + query(now << 1 | 1,mid + 1,r,mid + 1,y);
    if(right[now << 1] == left[now << 1 | 1])
        ans--;
    return ans;
    }
}

int update(int now,int l,int r,int x){
    if(l == r)
    return left[now];
    if(lazy[now])
    pushdown(now,l,r);
    int mid = (l + r) >> 1;
    if(x > mid)
    return update(now << 1 | 1,mid + 1,r,x);
    else
    return update(now << 1,l,mid,x);
}

int get_query(int x,int y) {
    int ans = 0,L,R;
    while(top[x] != top[y]) {
        if(dep[top[x]] > dep[top[y]])
            swap(x,y);
        ans += query(1,1,n,dfn[top[y]],dfn[y]);
    L = update(1,1,n,dfn[top[y]]);
    R = update(1,1,n,dfn[fa[top[y]]]);
        y = fa[top[y]];
    if(L == R)
        ans--;
    }
    if(dep[x] > dep[y])
        swap(x,y);
    ans += query(1,1,n,dfn[x],dfn[y]);
    if(ans)
        return ans;
    else
        return 1;
}

int main() {
    scanf("%d%d",&n,&m);
    for(int i = 1; i <= n; i++)
        scanf("%d",&col[i]);
    for(int i = 1; i < n; i++) {
        int a,b;
        scanf("%d%d",&a,&b);
        add(a,b);
        add(b,a);
    }
    cnt = 0;
    dfs1(1,0,1);
    dfs2(1,1);
    build(1,1,n);
    for(int i = 1; i <= m; i++) {
        char op[5];
        int l,r,c;
        scanf("%s",op);
        if(op[0] == 'C') {
            scanf("%d%d%d",&l,&r,&c);
            get_modify(l,r,c);
        }
        if(op[0] == 'Q') {
            scanf("%d%d",&l,&r);
        printf("%d\n",get_query(l,r));
        }
    }
    return 0;
}

ok啦

说起来

今天zzb就走了

我快乐!

然后突然发现没写过树剖和点分治的blog

咕咕咕万一以后写了呢emmmm