HDU 4747 Mex

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 200010;
 5 struct arc {
 6     int pos,next;
 7     arc(int x = 0,int y = -1) {
 8         pos = x;
 9         next = y;
10     }
11 } e[maxn<<2];
12 struct node {
13     LL sum;
14     int lazy,minv,maxv;
15 } tree[maxn<<2];
16 int head[maxn],a[maxn],tot,n;
17 void add(int u,int pos) {
18     e[tot] = arc(pos,head[u]);
19     head[u] = tot++;
20 }
21 inline void pushup(int v) {
22     tree[v].minv = min(tree[v<<1].minv,tree[v<<1|1].minv);
23     tree[v].maxv = max(tree[v<<1].maxv,tree[v<<1|1].maxv);
24     tree[v].sum = tree[v<<1].sum + tree[v<<1|1].sum;
25 }
26 inline void pushdown(int L,int R,int v) {
27     if(tree[v].lazy != -1) {
28         int mid = (L + R)>>1;
29         tree[v<<1].maxv = tree[v<<1].minv = tree[v].lazy;
30         tree[v<<1].sum = (LL)tree[v].lazy*(mid - L + 1);
31         tree[v<<1].lazy = tree[v].lazy;
32         tree[v<<1|1].maxv = tree[v<<1|1].minv = tree[v].lazy;
33         tree[v<<1|1].lazy = tree[v].lazy;
34         tree[v<<1|1].sum = (LL)tree[v].lazy*(R - mid);
35         tree[v].lazy = -1;
36     }
37 }
38 void build(int lt,int rt,int v) {
39     tree[v].lazy = -1;
40     if(lt == rt) {
41         tree[v].maxv = tree[v].minv = tree[v].sum = n - lt + 1;
42         return;
43     }
44     int mid = (lt + rt)>>1;
45     build(lt,mid,v<<1);
46     build(mid+1,rt,v<<1|1);
47     pushup(v);
48 }
49 void update(int L,int R,int lt,int rt,int val,int v) {
50     if(tree[v].maxv <= val) return;
51     if(lt <= L && rt >= R && tree[v].minv >= val) {
52         tree[v].maxv = tree[v].minv = val;
53         tree[v].sum = LL(val)*(R - L + 1);
54         tree[v].lazy = val;
55         return;
56     }
57     pushdown(L,R,v);
58     int mid = (L + R)>>1;
59     if(lt <= mid) update(L,mid,lt,rt,val,v<<1);
60     if(rt > mid) update(mid+1,R,lt,rt,val,v<<1|1);
61     pushup(v);
62 }
63 int main() {
64     while(scanf("%d",&n),n) {
65         memset(head,-1,sizeof head);
66         tot = 0;
67         for(int i = 1; i <= n; ++i) scanf("%d",a+i);
68         for(int i = n; i > 0; --i) if(a[i] <= n) add(a[i],i);
69         build(1,n,1);
70         LL ret = 0;
71         for(int i = 0; i <= n && tree[1].sum; ++i){
72             int last = 0;
73             for(int j = head[i]; ~j; j = e[j].next){
74                 update(1,n,last+1,e[j].pos, n - e[j].pos + 1,1);
75                 last = e[j].pos;
76             }
77             if(last < n) update(1,n,last + 1,n,0,1);
78             ret += tree[1].sum;
79         }
80         printf("%I64d\n",ret);
81     }
82     return 0;
83 }