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

 #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 ;

 }

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hdu 5273 Dylans loves sequence