线段树区间更新+区间合并

题目链接

一看就是线段树区间合并的题。

俩操作，一个跟新，一个查询

#include<stdio.h>#include<stdlib.h>#include<string.h>#include<math.h>#include<iostream>#include<algorithm>#include<stack>#include<queue>#include<string>#include<vector>#include<set>#include<map>#include<string>using namespace std;typedef long long ll;const int INF=0x3f3f3f3f;char str[1000010];struct node1{    int l,r,len,lazy;    int lb,rb,mb;    void Merge(int key)    {        if(key==1){lb=rb=mb=0;}        else {lb=rb=mb=len;}    }}node[1000010*4];void push_up(int n){    int lson=n*2,rson=n*2+1;    node[n].lb=node[lson].lb;    node[n].rb=node[rson].rb;    if(node[lson].lb==node[lson].len)node[n].lb+=node[rson].lb;    if(node[rson].rb==node[rson].len)node[n].rb+=node[lson].rb;    node[n].mb=max(max(node[rson].mb,node[lson].mb),node[lson].rb+node[rson].lb);}void push_down(int n){    if(node[n].lazy)    {        node[n*2].lazy=node[n*2+1].lazy=node[n].lazy;        node[n*2].Merge(node[n].lazy);node[n*2+1].Merge(node[n].lazy);        node[n].lazy=0;    }}void build(int l,int r,int n){    node[n].l=l,node[n].r=r,node[n].len=r-l+1,node[n].lazy=0;    if(l==r)    {        if(str[l]=='A')node[n].lb=node[n].rb=node[n].mb=0;        else if(str[l]=='B')node[n].lb=node[n].rb=node[n].mb=1;        return;    }    int mid=(l+r)/2;    build(l,mid,n*2);    build(mid+1,r,n*2+1);    push_up(n);}void update(int p,int q,int n,int k){    if(p<=node[n].l&&q>=node[n].r)    {node[n].lazy=k;node[n].Merge(k);return;}    push_down(n);    int mid=(node[n].l+node[n].r)/2;    if(p>=mid+1)update(p,q,n*2+1,k);    else if(q<=mid)update(p,q,n*2,k);    else{update(p,q,n*2,k);update(p,q,n*2+1,k);}    push_up(n);}node1 Merge_query(node1 p1,node1 p2){    node1 ans;    ans.len=p1.len+p2.len;    ans.lb=p1.lb;ans.rb=p2.rb;    if(p1.lb==p1.len) ans.lb+=p2.lb;    if(p2.rb==p2.len) ans.rb+=p1.rb;    ans.mb=max(max(p1.mb,p2.mb),p1.rb+p2.lb);    return ans;}node1 query(int p,int q,int n){    if(node[n].l>=p&&q>=node[n].r)return node[n];    push_down(n);    int mid=(node[n].l+node[n].r)/2;    if(p>=mid+1) return query(p,q,n*2+1);    else if(q<=mid) return query(p,q,n*2);    else{ return Merge_query(query(p,q,n*2),query(p,q,n*2+1));}}int main(){    int t;scanf("%d",&t);    for(int ca=1;ca<=t;ca++)    {        printf("Case #%d:\n",ca);int n,m;        scanf("%d%d",&n,&m);scanf("%s",str+1);        build(1,n,1);        while(m--)        {            int op,l,r,w;scanf("%d%d%d",&op,&l,&r);            if(op==1){scanf("%d",&w);update(l,r,1,w);}            else            {                node1 ans=query(l,r,1);                printf("%d\n",max(ans.lb,max(ans.rb,ans.mb)));            }        }    }    return 0;}