hdu5788 level up

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贴下以前写的代码
比赛前我准备着重看的
主席树树dp 字符串
#include<bits/stdc++.h>using namespace std;typedef long long ll;const int MAXN = 1e5+5;const int MOD = 1e9+7;int N;int A[MAXN];vector<int> mp[MAXN];int val[MAXN][2];/**********President Tree**********/int tot;struct Node{    int ls, rs, cc;    Node(int a=0, int b=0, int c=0):ls(a), rs(b), cc(c){}}tree[MAXN*20];int sta[MAXN];int Build(int pos,int l,int r){    int rt = tot++;    tree[rt].cc = 1;    tree[rt].ls = tree[rt].rs = 0;    if(l == r) return rt;    int mid = (l+r) >> 1;    if(pos <= mid) tree[rt].ls = Build(pos, l,mid);    else tree[rt].rs = Build(pos, mid+1,r);    return rt;}int Merge(int x,int y,int l,int r){    if(x == 0 || y == 0) return x+y;    tree[x].cc += tree[y].cc;    if(l == r) {        tree[x].ls = tree[x].rs = 0;        return x;    }        int mid = (l+r) >> 1;    tree[x].ls = Merge(tree[x].ls, tree[y].ls, l, mid);    tree[x].rs = Merge(tree[x].rs, tree[y].rs,mid+1, r);    return x;}int Query(int rt,int K,int l,int r){    if(tree[rt].cc < K) return 100000;    if(l == r) return l;    int mid = (l+r)>>1;    if(tree[tree[rt].ls].cc >= K) return Query(tree[rt].ls, K, l ,mid);    else return Query(tree[rt].rs, K-tree[tree[rt].ls].cc, mid+1, r);}void dfs(int x){    sta[x] = Build(A[x], 1, 100000);    for(int i = 0; i < mp[x].size(); ++i){        int y = mp[x][i];        dfs(y);        sta[x] = Merge(sta[x], sta[y], 1, 100000);    }//    printf("%d\n",sta[x]);    val[x][0] = Query(sta[x], tree[sta[x]].cc+1>>1, 1, 100000);    val[x][1] = Query(sta[x], (tree[sta[x]].cc+1>>1)+1, 1, 100000);}/**************BIT*************/ll bitt[MAXN];void Add(int pos,int num){    for(int i = pos; i > 0; i -= i&-i)        bitt[i] += num;}ll Sum(int pos){    ll ans = 0;    for(int i = pos; i <= 100000; i += i&-i)        ans += bitt[i];    return ans;}ll dfs2(int x){    Add(val[x][0], val[x][1]-val[x][0]);    ll ans = Sum(val[x][0]);    for(int i = 0; i < mp[x].size(); ++i){        int y = mp[x][i];        ans = max(ans, dfs2(y));    }    Add(val[x][0], val[x][0]-val[x][1]);    return ans;}int main(){    while(~scanf("%d",&N)){        memset(bitt,0,sizeof(bitt));        tot = 1;        for(int i = 1; i <= N; ++i) scanf("%d",&A[i]);        for(int i = 1; i <= N; ++i) mp[i].clear();        for(int i = 2; i <= N; ++i){            int a; scanf("%d",&a);            mp[a].push_back(i);        }        dfs(1);        ll sum = 0;        for(int i = 1; i <= N; ++i)             sum += val[i][0];        printf("%lld\n", sum + dfs2(1));    }    return 0;}
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