sopj 1716 Can you answer these queries III

题目链接:https://www.spoj.pl/problems/GSS3/

题目大意:求子序列的最大子序列和,且可单点更新某一值.

思路:和Can you answer these queries I一样,但是sum不能离线,需要在线段树中维护,因为值会被更新.

代码:

#include <stdlib.h>#include <string.h>#include <stdio.h>#include <ctype.h>#include <math.h>#include <time.h>#include <stack>#include <queue>#include <map>#include <set>#include <vector>#include <string>#include <iostream>#include <algorithm>using namespace std;//#define ull unsigned __int64//#define ll __int64#define ull unsigned long long#define ll long long#define son1 New(p.xl,xm,p.yl,ym),(rt<<2)-2#define son2 New(p.xl,xm,min(ym+1,p.yr),p.yr),(rt<<2)-1#define son3 New(min(xm+1,p.xr),p.xr,p.yl,ym),rt<<2#define son4 New(min(xm+1,p.xr),p.xr,min(ym+1,p.yr),p.yr),rt<<2|1#define lson l,mid,rt<<1#define rson mid+1,r,rt<<1|1#define middle (l+r)>>1#define MOD 1000000007#define esp (1e-8)const int INF=0x3F3F3F3F;const double DINF=10000.00;//const double pi=acos(-1.0);const int N=50010;int n,m,tot;ll lmax[N<<2],rmax[N<<2],mmax[N<<2],sum[N<<2];struct node{ll lmax,rmax,mmax,sum;};ll max(ll x,ll y){return x>y? x:y;}void func(ll& r,ll x,ll y,int& p,int xp,int yp){if(x>y) r=x,p=xp;else r=y,p=yp;}void pushUp(int rt){int ls=rt<<1,rs=ls|1;sum[rt]=sum[ls]+sum[rs];lmax[rt]=max(lmax[ls],sum[ls]+lmax[rs]);rmax[rt]=max(rmax[rs],sum[rs]+rmax[ls]);mmax[rt]=max(max(mmax[ls],mmax[rs]),rmax[ls]+lmax[rs]);}void build(int l,int r,int rt){if(l==r){scanf("%lld",&sum[rt]);lmax[rt]=mmax[rt]=rmax[rt]=sum[rt];return;}int mid=middle;build(lson),build(rson);pushUp(rt);}node query(int l,int r,int rt,int L,int R){if(L<=l && r<=R){node ret;ret.sum=sum[rt];ret.lmax=lmax[rt];ret.rmax=rmax[rt];ret.mmax=mmax[rt];return ret;}int mid=middle;if(R<=mid) return query(lson,L,R);if(mid<L) return query(rson,L,R);node lret=query(lson,L,mid);node rret=query(rson,mid+1,R);node ret;ret.sum=lret.sum+rret.sum;ret.lmax=max(lret.lmax,lret.sum+rret.lmax);ret.rmax=max(rret.rmax,rret.sum+lret.rmax);ret.mmax=max(max(lret.mmax,rret.mmax),lret.rmax+rret.lmax);return ret;}void update(int l,int r,int rt,int p,ll c){if(l==r){lmax[rt]=mmax[rt]=rmax[rt]=sum[rt]=c;return;}int mid=middle;if(p<=mid) update(lson,p,c);else update(rson,p,c);pushUp(rt);}void init(){sum[0]=0;build(1,n,1);scanf("%d",&m);}void sof(){int i,x,y;while(m--){scanf("%d%d%d",&i,&x,&y);if(i) printf("%lld\n",query(1,n,1,x,y).mmax);else update(1,n,1,x,(ll)y);}}int main(){//freopen("1.in","r",stdin);//freopen("no pos.out","w",stdout);//int T,cas;scanf("%d",&T);for(cas=1;cas<=T;cas++){while(~scanf("%d",&n)){init(),sof();}return 0;}