线段树进阶---森森快递

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;
}