L3-017 森森快递 (30分)
题目链接
团体程序设计天梯赛练习题–森森快递
AC代码
#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
#define MAX 100010
typedef struct point
{
int x;
int y;
}Point;
typedef struct
{
int left;
int right;
long long val;
long long lazy;
}Node;
Node node[MAX * 4];
vector<Point> vec;
long long num[MAX];
int n,q;
void built(int root,int left,int right)
{
node[root].lazy=0;
node[root].left=left;
node[root].right=right;
if(left==right)
{
node[root].val=num[left];
return ;
}
int mid=(left+right)/2;
int left_node=root *2 +1;
int right_node=root * 2+2;
built(left_node,left,mid);
built(right_node,mid+1,right);
node[root].val=min(node[left_node].val,node[right_node].val);
}
void pushdown(int root)
{
if(node[root].lazy)
{
node[root * 2 + 1].lazy+=node[root].lazy;
node[root * 2 + 2].lazy+=node[root].lazy;
node[root * 2 + 1].val+=node[root].lazy;
node[root * 2 + 2].val+=node[root].lazy;
node[root].lazy=0;
}
}
long long query(int root,int left,int right)
{
if(left<=node[root].left && right >=node[root].right) return node[root].val;
int mid=(node[root].left+node[root].right)/2;
if(node[root].lazy) pushdown(root);
if(right<=mid) return query(root*2+1,left,right);
else if(left>mid) return query(root*2+2,left,right);
else return min(query(root*2+1,left,right),query(root*2+2,left,right));
}
void update(int root,int left,int right,long long val)
{
if(left<=node[root].left && right>=node[root].right)
{
node[root].val+=val;
node[root].lazy+=val;
return;
}
if(node[root].lazy) pushdown(root);
int mid=(node[root].left+node[root].right)/2;
if(right<=mid) update(root*2+1,left,right,val);
else if(left>mid) update(root * 2 +2,left,right,val);
else
{
update(root*2+1,left,right,val);
update(root * 2 +2,left,right,val);
}
node[root].val=min(node[root*2+1].val,node[root*2+2].val);
}
bool cmp(Point a,Point b)
{
if(a.y!=b.y) return a.y<b.y;
else return a.x<b.x;
}
int main()
{
cin>>n>>q;
long long ans=0,cur=0;
for(int i=0;i<n-1;i++) cin>>num[i];
built(0,0,n-2);
for(int i=0;i<q;i++)
{
int a,b;
cin>>a>>b;
if(a>b) swap(a,b);
Point p;
p.x=a;
p.y=b;
vec.push_back(p);
}
sort(vec.begin(),vec.end(),cmp);
for(int i=0;i<q;i++)
{
int a,b;
a=vec[i].x;
b=vec[i].y;
cur=query(0,a,b-1);
ans+=cur;
if(cur!=0)
update(0,a,b-1,-cur);
}
cout<<ans;
return 0;
}