1 #include<stdio.h>
2 #include<string.h>
3 #define MOD 1000000007
4 __int64 ans[100005],c[100005];
5 int a[100005],wei[100005],n;
6 void sort(int l,int r)
7 {
8 int i,j,x,y,x1;
9 x=a[(l+r)/2]; x1=wei[(l+r)/2];
10 i=l; j=r;
11 while (i<=j)
12 {
13 while (a[i]<x||(a[i]==x&&wei[i]<x1)) i++;
14 while (x<a[j]||(a[j]==x&&wei[j]>x1)) j--;
15 if (i<=j)
16 {
17 y=a[i]; a[i]=a[j]; a[j]=y;
18 y=wei[i]; wei[i]=wei[j]; wei[j]=y;
19 i++; j--;
20 }
21 }
22 if (i<r) sort(i,r);
23 if (l<j) sort(l,j);
24 }
25 int lowbit(int x)
26 {
27 return(x&(-x));
28 }
29 __int64 sum(int x)
30 {
31 __int64 ret=0;
32 while (x>0){
33 ret=(ret+c[x])%MOD;
34 x-=lowbit(x);
35 }
36 return ret;
37 }
38 void add(int x,__int64 d)
39 {
40 while (x<=n){
41 c[x]=(c[x]+d)%MOD;
42 x+=lowbit(x);
43 }
44 }
45 int main()
46 {
47 int i;
48 __int64 aa;
49 while (~scanf("%d",&n))
50 {
51 for (i=1;i<=n;i++)
52 {
53 scanf("%d",&a[i]);
54 ans[i]=1; wei[i]=i;
55 }
56 sort(1,n);
57 memset(c,0,sizeof(c));
58 for (i=1;i<=n;i++)
59 {
60 ans[wei[i]]=(1+sum(wei[i]-1))%MOD;
61 add(wei[i],ans[wei[i]]);
62
63 }
64 printf("%I64d\n",sum(n));
65 }
66 }
http://acm.hdu.edu.cn/showproblem.php?pid=2227
