hdu5316 Magician(线段树区间合并)

#include<iostream>
#include<cstdio>
#include<cstring>
#define LL __int64
#define lson rt<<1
#define rson rt<<1|1
using namespace std;

const int N=100100;
const LL INF=0x3f3f3f3f3f3f3f3f;

//子序列情况：奇始奇终、奇始偶终、偶始奇终、偶始偶终
struct Node
{
int l,r;
LL oo,ee,oe,eo;
int Mid(){return (l+r)/2;}
}tree[4*N];

LL num
;

LL Max(LL a,LL b)
{
return a<b ?b :a;
}

void pushUp(int rt)
{
LL a=tree[lson].oe+tree[rson].oe;
LL b=tree[lson].eo+tree[rson].eo;
LL c=tree[lson].ee+tree[rson].oo;
LL d=tree[lson].oo+tree[rson].ee;

LL e=tree[lson].oe+tree[rson].oo;
LL f=tree[lson].oo+tree[rson].eo;
LL g=tree[lson].ee+tree[rson].oe;
LL h=tree[lson].eo+tree[rson].ee;

tree[rt].oe=Max(Max(a,d),Max(tree[lson].oe,tree[rson].oe));
tree[rt].eo=Max(Max(b,c),Max(tree[lson].eo,tree[rson].eo));
tree[rt].oo=Max(Max(e,f),Max(tree[lson].oo,tree[rson].oo));
tree[rt].ee=Max(Max(g,h),Max(tree[lson].ee,tree[rson].ee));
}

Node query(int rt,int l,int r)
{
Node temp,t1,t2;
if(tree[rt].l==l&&tree[rt].r==r){
temp.eo=tree[rt].eo;
temp.ee=tree[rt].ee;
temp.oe=tree[rt].oe;
temp.oo=tree[rt].oo;
return temp;
}
if(r<=tree[rt].Mid()){
return query(lson,l,r);
}
else if(l>tree[rt].Mid()){
return query(rson,l,r);
}
else{
t1=query(lson,l,tree[rt].Mid());
t2=query(rson,tree[rt].Mid()+1,r);
temp.oe=Max(Max(t1.oe+t2.oe,t1.oo+t2.ee),Max(t1.oe,t2.oe));
temp.eo=Max(Max(t1.eo+t2.eo,t1.ee+t2.oo),Max(t1.eo,t2.eo));
temp.oo=Max(Max(t1.oe+t2.oo,t1.oo+t2.eo),Max(t1.oo,t2.oo));
temp.ee=Max(Max(t1.eo+t2.ee,t1.ee+t2.oe),Max(t1.ee,t2.ee));
return temp;
}
}

void update(int rt,int x,int v)
{
if(tree[rt].l==x&&tree[rt].r==x){
if(x&1){
tree[rt].oo=v;
}
else{
tree[rt].ee=v;
}
return;
}
if(x<=tree[rt].Mid()){
update(2*rt,x,v);
}
else{
update(2*rt+1,x,v);
}
pushUp(rt);
}

void build(int rt,int l,int r)
{
tree[rt].l=l;tree[rt].r=r;
if(l==r){
if(l&1){
tree[rt].oo=num[l];
tree[rt].ee=-INF;
}
else{
tree[rt].oo=-INF;
tree[rt].ee=num[l];
}
tree[rt].eo=-INF;
tree[rt].oe=-INF;
return;
}
int mid=(l+r)/2;
build(2*rt,l,mid);
build(2*rt+1,mid+1,r);
//向上合并
pushUp(rt);
}

int main()
{
//freopen("d:\\Test.txt","r",stdin);
int T;
int n,m;
LL ans;
scanf("%d",&T);
while(T--){
scanf("%d%d",&n,&m);
for(int i=1;i<=n;i++){
scanf("%I64d",&num[i]);
}
build(1,1,n);
for(int i=1;i<=m;i++){
int op,a,b;
scanf("%d%d%d",&op,&a,&b);
if(op==0){
Node res=query(1,a,b);
ans=Max(Max(res.ee,res.oo),Max(res.eo,res.oe));
printf("%I64d\n",ans);
}
else if(op==1){
update(1,a,b);
}
}
}
return 0;
}