codeforces 413E 线段树

#include<cstdio>
#include<algorithm>
#include<cstring>
#define fo(i,a,b) for(int i=a;i<=b;i++)
#define fd(i,a,b) for(int i=a;i>=b;i--)
using namespace std;
const int N=2e5+5;
const int inf=1e9;
int n,m;
int mp[3]
;
char ch
;
struct node
{
int d1,d2,d3,d4;
};
struct tree
{
int l,r;
node d;
}t[N*5];
node merge(node a,node b)
{
node tmp;
tmp.d1=min(inf,min(a.d1+b.d1,a.d2+b.d3)+1);
tmp.d2=min(inf,min(a.d1+b.d2,a.d2+b.d4)+1);
tmp.d3=min(inf,min(a.d3+b.d1,a.d4+b.d3)+1);
tmp.d4=min(inf,min(a.d3+b.d2,a.d4+b.d4)+1);
return tmp;
}
inline void build(int x,int l,int r)
{
t[x].l=l,t[x].r=r;
if (l==r)
{
t[x].d.d1=t[x].d.d2=t[x].d.d3=t[x].d.d4=inf;
if (mp[1][l])t[x].d.d1=0;
if (mp[2][l])t[x].d.d4=0;
if (mp[1][l]&&mp[2][l])t[x].d.d2=t[x].d.d3=1;
return;
}
int mid=(l+r)>>1;
build(x<<1,l,mid);
build(x<<1|1,mid+1,r);
t[x].d=merge(t[x<<1].d,t[x<<1|1].d);
}
inline node query(int x,int l,int r)
{
if (l==t[x].l&&r==t[x].r)return t[x].d;
int mid=(t[x].l+t[x].r)>>1;
if (r<=mid)return query(x<<1,l,r);
else if (l>mid)return query(x<<1|1,l,r);
else return merge(query(x<<1,l,mid),query(x<<1|1,mid+1,r));
}
inline int ask(int x,int y)
{
int a=(x-1)%n+1,b=(y-1)%n+1;
if (a>b)
{
swap(x,y);
swap(a,b);
}
node tmp=query(1,a,b);
if (x<=n&&y<=n)return tmp.d1;
if (x<=n&&y>n)return tmp.d2;
if (x>n&&y<=n)return tmp.d3;
if (x>n&&y>n)return tmp.d4;
}
int main()
{
scanf("%d%d",&n,&m);
fo(i,1,2)
{
scanf("%s",ch);
fo(j,1,n)
if (ch[j-1]=='.')mp[i][j]=1;
}
build(1,1,n);
fo(i,1,m)
{
int x,y;
scanf("%d%d",&x,&y);
int ans=ask(x,y);
if (ans<inf)printf("%d\n",ans);
else printf("-1\n");
}
return 0;
}