[HDU 4747] Mex （线段树）

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <set>
 5 using namespace std;
 6 
 7 typedef long long LL;
 8 typedef pair<int,int> PII;
 9 const int MAX_N = 2e5+100;
10 LL delta[MAX_N<<2],sum[MAX_N<<2],maxn[MAX_N<<2];
11 PII b[MAX_N];
12 int a[MAX_N],next[MAX_N],n;
13 set<int> Set;
14 
15 void push_down(int idx,int l,int r){
16     if( delta[idx]!=-1 ){
17         int m = l+r>>1;
18         sum[idx<<1] = (m-l+1)*delta[idx];
19         sum[idx<<1|1] = (r-m)*delta[idx];
20         delta[idx<<1] = delta[idx<<1|1] = maxn[idx<<1] = maxn[idx<<1|1] = delta[idx];
21         delta[idx] = -1;
22     }
23 }
24 
25 void push_up(int idx){
26     sum[idx] = sum[idx<<1]+sum[idx<<1|1];
27     maxn[idx] = max(maxn[idx<<1],maxn[idx<<1|1]);
28 }
29 
30 void update(int L,int R,LL x,int idx,int l,int r){
31     if( R<l||L>r ) return;
32     if( L<=l&&R>=r ) {
33         sum[idx]  = (r-l+1)*x;
34         maxn[idx] = delta[idx] = x;
35         return;
36     }
37     push_down(idx,l,r);
38     int m = l+r>>1;
39     if( L<=m ) update(L,R,x,idx<<1,l,m);
40     if( R>m ) update(L,R,x,idx<<1|1,m+1,r);
41     push_up(idx);
42 }
43 
44 int query(LL x,int idx,int l,int r){
45     if( maxn[idx]<=x ) return r+1;
46     if( l==r ) return l;
47     push_down(idx,l,r);
48     int m = l+r>>1;
49     if( maxn[idx<<1]>x ) return query(x,idx<<1,l,m);
50     else return query(x,idx<<1|1,m+1,r);
51 }
52 
53 LL querySum(int L,int R,int idx,int l,int r){
54     if( L<=l&&R>=r ) return sum[idx];
55     push_down(idx,l,r);
56     int m = l+r >> 1 ;
57     LL res = 0;
58     if( L<=m ) res =  querySum(L,R,idx<<1,l,m);
59     if( R>m ) res += querySum(L,R,idx<<1|1,m+1,r);
60     return res;
61 }
62 
63 int main(){
64     while(scanf("%d",&n)!=EOF&&n){
65         memset(sum,0,sizeof(sum));
66         memset(delta,-1,sizeof(delta));
67         Set.clear();
68         for(int i=1;i<=n;i++){
69             scanf("%d",&a[i]);
70             b[i] = PII(a[i],i);
71             next[i] = n+1;
72         }
73         sort(b+1,b+1+n);
74         b[n+1].first = b[n].first; b[n+1].second = n+1;
75         for(int i=1;i<=n;i++){
76             if( b[i].first==b[i+1].first ) next[b[i].second] = b[i+1].second;
77         }
78         int mmex = 0;
79         for(int i=1;i<=n;i++){
80             Set.insert(a[i]);
81             while( Set.find(mmex)!=Set.end() ) mmex++;
82             update(i,i,mmex,1,1,n);
83         }
84         LL ans = sum[1];
85         for (int l = 1; l <= n; l++) {
86             update(l,l,0,1,1,n);
87             int p = query(a[l],1,1,n);
88             p = max(l+1,p);
89             int q = next[l] - 1;
90             update(p,q,a[l],1,1,n);
91             ans += sum[1];
92         }
93         printf("%I64d\n", ans);
94     }
95     return 0;
96 }