Merge line segments in the HDU 3911 black and white intervals

Question: it is important to find the longest one in a certain interval.

#include<cstdio>#include<cstring>#define left l,m,x<<1#define right m+1,r,x<<1|1const int LMT=100004;int ox[LMT<<2],lsum[2][LMT<<2],msum[2][LMT<<2],rsum[2][LMT<<2];void init(void){    memset(msum,0,sizeof(msum));    memset(lsum,0,sizeof(lsum));    memset(rsum,0,sizeof(rsum));    memset(ox,0,sizeof(ox));}inline int max(int a,int b){    return a>b?a:b;}void swap(int &a,int &b){    int t=a;    a=b;    b=t;}void fox(int l,int r,int x){    ox[x]^=1;    swap(lsum[0][x],lsum[1][x]);    swap(rsum[0][x],rsum[1][x]);    swap(msum[0][x],msum[1][x]);}void cut(int l,int r,int x){    int m=(l+r)>>1;    if(ox[x])    {        fox(right);fox(left);        ox[x]=0;    }}void pushup(int pos,int x,int len){    lsum[pos][x]=lsum[pos][x<<1];    rsum[pos][x]=rsum[pos][x<<1|1];    if(lsum[pos][x<<1]==len-(len>>1))lsum[pos][x]+=lsum[pos][x<<1|1];    if(rsum[pos][x<<1|1]==len>>1)rsum[pos][x]+=rsum[pos][x<<1];    msum[pos][x]=max(rsum[pos][x<<1]+lsum[pos][x<<1|1],max(msum[pos][x<<1],msum[pos][x<<1|1]));}void update(int L,int R,int l,int r,int x){    if(L<=l&&r<=R)    {        fox(l,r,x);        return;    }    cut(l,r,x);    int m=(l+r)>>1;    if(L<=m)update(L,R,left);    if(R>m)update(L,R,right);    pushup(0,x,r-l+1);    pushup(1,x,r-l+1);}void query(int *res,int L,int R,int l,int r,int x){    if(L<=l&&r<=R)    {        res[0]=lsum[1][x];        res[1]=msum[1][x];        res[2]=rsum[1][x];        return;    }    int resl[3],resr[3],m=(l+r)>>1,len=r-l+1;    memset(resl,0,sizeof(resl));    memset(resr,0,sizeof(resr));    cut(l,r,x);    if(L<=m)query(resl,L,R,left);    if(R>m)query(resr,L,R,right);    res[0]=resl[0];res[2]=resr[2];    if(resl[0]==len-(len>>1))res[0]+=resr[0];    if(resr[2]==len>>1)res[2]+=resl[2];    res[1]=max(resl[2]+resr[0],max(resl[1],resr[1]));}void build(int l,int r,int x){    if(l==r)    {        int num;        scanf("%d",&num);        msum[1][x]=lsum[1][x]=rsum[1][x]=num;        lsum[0][x]=msum[0][x]=rsum[0][x]=(num==0);        return;    }    int m=(l+r)>>1;    build(left);    build(right);    pushup(0,x,r-l+1);    pushup(1,x,r-l+1);}int main(void){    int n,m,op,l,r,have[3];    while(~scanf("%d",&n))    {        init();        build(0,n-1,1);        scanf("%d",&m);        while(m--)        {            scanf("%d%d%d",&op,&l,&r);            l--;r--;            if(op)update(l,r,0,n-1,1);            else            {                memset(have,0,sizeof(have));                query(have,l,r,0,n-1,1);                printf("%d\n",have[1]);            }        }    }    return 0;}