HDU 5273 Dylans loves sequence【 树状数组 】

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 using namespace std;
12 
13 typedef long long LL;
14 const int INF = (1<<30)-1;
15 const int mod=1000000007;
16 const int maxn=1005;
17 
18 int a[maxn];
19 int c[maxn];//树状数组
20 int n,m;
21 int ans[maxn][maxn];
22 
23 struct node{
24     int x,id;
25 }p[maxn];
26 
27 int cmp(node n1,node n2){
28     return n1.x < n2.x;
29 }
30 
31 int lowbit(int x){ return x &(-x);}
32 
33 int sum(int x){
34     int ret=0;
35     while(x>0){ 
36         ret += c[x];x-=lowbit(x); 
37     }
38     return ret;
39 }
40 
41 void add(int x,int d){
42     while(x<=n){
43         c[x]+=d;x+=lowbit(x);
44     }
45 }
46 
47 int main(){
48     while(scanf("%d %d",&n,&m) != EOF){
49         memset(c,0,sizeof(c));
50         memset(a,0,sizeof(a));
51         memset(ans,0,sizeof(ans));
52         for(int i=1;i<=n;i++) {
53             scanf("%d",&p[i].x);
54             p[i].id=i;
55         }
56         sort(p+1,p+n+1,cmp);
57         for(int i=1,j=0;i<=n;i++){
58             if(i==1||p[i].x != p[i-1].x) j++;
59             a[p[i].id]=j;
60         }
61         
62     //    for(int i=1;i<=n;i++)
63     //    printf("a[%d]=%d\n",i,a[i]);
64         
65         for(int i=1;i<=n;i++){
66             memset(c,0,sizeof(c));
67             int res=0;
68             for(int j=i;j<=n;j++){
69                 res+=(j-i)-sum(a[j]);
70                 add(a[j],1);
71                 ans[i][j] = res;
72             }
73         }
74     
75         while(m--){
76             int l,r;
77             scanf("%d %d",&l,&r);
78             printf("%d\n",ans[l][r]);
79         }
80     } 
81     return 0;
82 }