CF413E Maze 2D（线段树）

一个节点代表一个矩阵(1,l,2,r)。维护四个信息:四个角之间的最小距离，到不了就是inf，使得这四个信息具有可加性。即可用线段树进行维护。

#include <bits/stdc++.h>#define N 200010#define inf 0x3f3f3f3f inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}inline int min(int x,int y){return x<y?x:y;}inline int max(int x,int y){return x>y?x:y;}inline int swap(int &x,int &y){x^=y;y^=x;x^=y;}int n,m;bool map[3][N];struct data{    int d[5];//d1->(1,l)-(1,r) d2->(1,l)-(2,r) d3->(2,l)-(1,r) d4->(2,l)-(2,r)    data(){memset(d,0,sizeof(d));}    data operator+(data b){        data res;        res.d[1]=min(inf,min(d[1]+b.d[1]+1,d[2]+b.d[3]+1));        res.d[2]=min(inf,min(d[2]+b.d[4]+1,d[1]+b.d[2]+1));        res.d[3]=min(inf,min(d[3]+b.d[1]+1,d[4]+b.d[3]+1));        res.d[4]=min(inf,min(d[4]+b.d[4]+1,d[3]+b.d[2]+1));        return res;    }};struct segtree{    data d;}tree[N<<2];inline void pushup(int p){    tree[p].d=tree[p<<1].d+tree[p<<1|1].d;}void build(int p,int l,int r){    if(l==r){        memset(tree[p].d.d,0x3f,sizeof(tree[p].d.d));        if(map[1][l]) tree[p].d.d[1]=0;        if(map[2][l]) tree[p].d.d[4]=0;        if(map[1][l]&&map[2][l]) tree[p].d.d[2]=tree[p].d.d[3]=1;        return;    }    int mid=l+r>>1;    build(p<<1,l,mid);build(p<<1|1,mid+1,r);    pushup(p);}data query(int p,int l,int r,int x,int y){    if(x<=l&&r<=y) return tree[p].d;    int mid=l+r>>1;    if(y<=mid) return query(p<<1,l,mid,x,y);    else if(x>mid)  return query(p<<1|1,mid+1,r,x,y);    else return query(p<<1,l,mid,x,y)+query(p<<1|1,mid+1,r,x,y);}int ask(int x,int y){    int l=(x-1)%n+1,r=(y-1)%n+1;    if(l>r) swap(l,r),swap(x,y);    data res=query(1,1,n,l,r);    if(x<=n&&y<=n) return res.d[1];    if(x<=n&&y>n) return res.d[2];    if(x>n&&y<=n) return res.d[3];    if(x>n&&y>n) return res.d[4];}int main(){//  freopen("a.in","r",stdin);    n=read();m=read();    for(int i=1;i<=2;++i){        char s[N];scanf("%s",s+1);        for(int j=1;j<=n;++j) if(s[j]=='.') map[i][j]=1;    }build(1,1,n);    while(m--){        int x=read(),y=read();        int ans=ask(x,y);        printf("%d\n",ans==inf?-1:ans);    }    return 0;}