hdu 5273 Dylans loves sequence

题目连接

http://acm.hdu.edu.cn/showproblem.php?pid=5273

Dylans loves sequence

Description

Dylans is given $N$ numbers $a[1]....a[N]$

And there are $Q$ questions.

Each question is like this $(L,R)$

his goal is to find the “inversions” from number $L$ to number $R.$

more formally,his needs to find the numbers of pair$（x,y）$,
that $L \leq x,y \leq R$ and $ x < y $ and $a[x] > a[y]$

Input

In the first line there is two numbers $N$ and $Q.$

Then in the second line there are $N$ numbers:$a[1]..a[N]$

In the next $Q$ lines,there are two numbers $L,R$ in each line.

$N \leq 1000, Q \leq 100000, L \leq R, 1 \leq a[i] \leq 2^{31}-1$

Output

For each query,print the numbers of "inversions”

SampleInput

3 2
3 2 1
1 2
1 3

SampleOutput

1

3

 #include<algorithm>
 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 #include<cstdio>
 #include<vector>
 #include<map>
 #include<set>
 using std::cin;
 using std::cout;
 using std::endl;
 using std::find;
 using std::sort;
 using std::set;
 using std::map;
 using std::pair;
 using std::vector;
 #define sz(c) (int)(c).size()
 #define all(c) (c).begin(), (c).end()
 #define iter(c) __typeof((c).begin())
 #define cls(arr,val) memset(arr,val,sizeof(arr))
 #define cpresent(c, e) (find(all(c), (e)) != (c).end())
 #define rep(i, n) for (int i = 0; i < (int)(n); i++)
 #define fork(i, k, n) for(int i = (int)k; i<= (int)n; i++)
 #define forp(i, k, p) for(int i = (int)k; i > p; i--)
 #define tr(c, i) for (iter(c) i = (c).begin(); i != (c).end(); ++i)
 #define pb(e) push_back(e)
 #define mp(a, b) make_pair(a, b)
 const int Max_N = ;
 typedef unsigned long long ull;
 int dp[Max_N][Max_N], arr[Max_N];
 int main() {
 #ifdef LOCAL
     freopen("in.txt","r",stdin);
     freopen("out.txt","w+",stdout);
 #endif
     int n, q, x, y;
     while(~scanf("%d %d",&n, &q)) {
         rep(i,n) scanf("%d",&arr[i + ]);
         cls(dp, );
         fork(i, , n) {
             fork(j, i + , n) dp[i][j] += dp[i][j - ] + (int)(arr[i] > arr[j]);
         }
         forp(j, n, ) {
             forp(i, j ,) dp[i][j] += dp[i + ][j];
         }
         rep(i, q) scanf("%d %d",&x, &y), printf("%d\n",dp[x][y]);
     }
     return ;
 }