GSS1
segment tree
#include <iostream>
#include <stdio.h>
using namespace std;
struct node
{
long bestSum, leftSum, rightSum, totalSum;
};
int n;
long t;
node seg[200003];
long arr[50003];
node combine(node &lc, node &rc)
{
node temp;
temp.totalSum = lc.totalSum + rc.totalSum;
temp.leftSum = max(lc.leftSum, lc.totalSum + rc.leftSum);
temp.rightSum = max(rc.rightSum, rc.totalSum + lc.rightSum);
temp.bestSum = max(lc.rightSum + rc.leftSum, max(lc.bestSum, rc.bestSum));
return temp;
}
void buildTree(int l, int r, int index)
{
if(l == r)
{
seg[index].bestSum = seg[index].rightSum = seg[index].leftSum = seg[index].totalSum = arr[l];
}
else
{
int mid = l + ((r - l) >> 1);
int lchild = (index << 1) + 1;
int rchild = (index << 1) + 2;
buildTree(l, mid, lchild);
buildTree(mid + 1, r, rchild);
seg[index] = combine(seg[lchild], seg[rchild]);
}
}
node query(int l, int r, int qs, int qe, int index)
{
if(qs <= l && qe >= r)
return seg[index];
int mid = l + ((r - l) >> 1);
int lchild = (index << 1) + 1;
int rchild = (index << 1) + 2;
if(qe <= mid)
return query(l, mid, qs, qe, lchild);
if(qs > mid)
return query(mid + 1, r, qs, qe, rchild);
node lc = query(l, mid, qs, qe, lchild);
node rc = query(mid + 1, r, qs, qe, rchild);
return combine(lc, rc);
}
int main()
{
int m, x, y;
scanf("%d",&n);
for(int i = 0; i < n; i++)
scanf("%ld",&arr[i]);
buildTree(0, n - 1, 0);
scanf("%d",&m);
for(int i = 0; i < m; i++)
{
scanf("%d",&x);
scanf("%d",&y);
t = query(0, n - 1, x - 1, y - 1, 0).bestSum;
printf("%ld\n", t);
}
return 0;
}
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