SPOJ GSS1 Can you answer these queries I

Can you answer these queries I

Time Limit: 1000ms
Memory Limit: 262144KB
This problem will be judged on SPOJ. Original ID: GSS1
64-bit integer IO format: %lld Java class name: Main

You are given a sequence $A[1], A[2], ..., A
$. $( |A[i]| \leq 15007 , 1\leq N \leq 50000 )$. A query is defined as follows:
$Query(x,y) = Max \{ a[i]+a[i+1]+...+a[j] ; x \leq i \leq j \leq y \}$.
Given M queries, your program must output the results of these queries.

Input

The first line of the input file contains the integer N.

In the second line, N numbers follow.

The third line contains the integer M.

M lines follow, where line i contains 2 numbers xi and yi.

Output

Your program should output the results of the M queries, one query per line.

Example

Input:
3
-1 2 3
1
1 2
Output:
2

解题：线段树

#include <bits/stdc++.h>
using namespace std;
const int maxn = 50010;
struct node{
int lt,rt,lsum,rsum,sum,msum;
}tree[maxn<<2];
inline void pushup(int v){
tree[v].sum = tree[v<<1].sum + tree[v<<1|1].sum;
tree[v].lsum = max(tree[v<<1].lsum,tree[v<<1].sum + tree[v<<1|1].lsum);
tree[v].rsum = max(tree[v<<1|1].rsum,tree[v<<1|1].sum + tree[v<<1].rsum);
tree[v].msum = max(max(tree[v<<1].msum,tree[v<<1|1].msum),tree[v<<1].rsum + tree[v<<1|1].lsum);
}
void build(int lt,int rt,int v){
tree[v].lt = lt;
tree[v].rt = rt;
if(lt == rt){
scanf("%d",&tree[v].sum);
tree[v].msum = tree[v].lsum = tree[v].rsum = tree[v].sum;
return;
}
int mid = (lt + rt)>>1;
build(lt,mid,v<<1);
build(mid + 1,rt,v<<1|1);
pushup(v);
}
node query(int lt,int rt,int v){
if(lt <= tree[v].lt && rt >= tree[v].rt) return tree[v];
int mid = (tree[v].lt + tree[v].rt)>>1;
if(rt <= mid) return query(lt,rt,v<<1);
if(lt > mid) return query(lt,rt,v<<1|1);
node a = query(lt,rt,v<<1);
node b = query(lt,rt,v<<1|1);
node c;
c.sum = a.sum + b.sum;
c.lsum = max(a.lsum,a.sum + b.lsum);
c.rsum = max(b.rsum,b.sum + a.rsum);
c.msum = max(max(a.msum,b.msum),a.rsum + b.lsum);
return c;
}
int main(){
int n,m,x,y;
while(~scanf("%d",&n)){
build(1,n,1);
scanf("%d",&m);
while(m--){
scanf("%d%d",&x,&y);
node d = query(x,y,1);
printf("%d\n",max(max(d.sum,d.msum),max(d.lsum,d.rsum)));
}
}
return 0;
}

View Code