Bestcoder Round #16 Revenge of Segment trees (tree-like array)

The first time today to participate in BC, although due to the movement will delay time, but still began to do the topic.

The first question happens to be a recently done tree array type, NLOGN complexity. The rule calculation is simple. The middle part is eliminated during the interval accumulation of a length, and the change in interval length causes the partial change to be subtracted. Minus is the front k-1, plus the back n-k+1 a

The second question has not been very well understood test instructions, although thought is not difficult.

At first did not overflow two times with a long long, O (︶^︶) o ay later see the mold and the like directly ll

#include <cstdio> #include <string> #include <string.h> #include <iostream> #include < algorithm> #include <map> #include <iterator>using namespace std;typedef __int64 ll; #define N 10+447000# Define MAX (a) > (b)? (        A):(B)) #define LOWBIT (x) (-X) &x#define MOD 1000000007int n,m;ll a[n];void Update (int l,int n) {while (l<n) {        a[l]= (a[l]+n)%mod;    L+=lowbit (l);    }}ll sum (int l) {ll ans=0;        while (l>0) {ans= (A[l]+ans)%mod;    L-=lowbit (l); } return ans;    int main () {int i,k;        int T;    Freopen ("In.txt", "R", stdin);        while (~SCANF ("%d", &t)) while (t--) {memset (a,0,sizeof (a));        scanf ("%d", &n);            for (i=1;i<=n;i++) {scanf ("%d", &k);        Update (I,K);        } ll Ans=0;        ll Sub=0;        ll Add=0;            for (k=1;k<=n;k++) {sub= (sum (k-1) +sub)%mod;            add= (SUM (n-k+1) +add)%mod; Ans= (add-sub+ans+mod)%mod;    } printf ("%i64d\n", ans); } return 0;}

Bestcoder Round #16 Revenge of Segment trees (tree-like array)