BZOJ1103(POI2007)[大都市meg]--DFS序+树状数组

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【链接】
bzoj1103

【解题报告】

DFS序+树状数组(或线段树)

#include<cstdio>#include<cstring>using namespace std;const int maxn=250005,maxm=500005;int n,m,tot,Time,c[maxm],lnk[maxn],son[maxm],nxt[maxm],in[maxn],out[maxn],fa[maxn];inline char nc(){    static char buf[100000],*l,*r;    if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);    if (l==r) return EOF; return *l++;}inline int Read(){    int res=0,f=1; char ch=nc(),cc=ch;    while (ch<'0'||ch>'9') cc=ch,ch=nc();    if (cc=='-') f=-1;    while (ch>='0'&&ch<='9') res=res*10+ch-48,ch=nc();    return res*f;}void Add(int x,int y) {son[++tot]=y; nxt[tot]=lnk[x]; lnk[x]=tot;}void Dfs(int x,int Fa){    in[x]=++Time; fa[x]=Fa;    for (int j=lnk[x]; j; j=nxt[j])     if (son[j]!=Fa) Dfs(son[j],x);    out[x]=++Time;}int Lowbit(int x) {return x&(-x);}void AddT(int x,int da) {while (x<=2*n) c[x]+=da,x+=Lowbit(x);}int GetT(int x) {int sum=0; while (x) sum+=c[x],x-=Lowbit(x); return sum;}int main(){    freopen("1103.in","r",stdin);    freopen("1103.out","w",stdout);    n=Read(); tot=Time=0;    memset(lnk,0,sizeof(lnk));    for (int i=1,x,y; i<n; i++) x=Read(),y=Read(),Add(x,y),Add(y,x);    Dfs(1,0);    memset(c,0,sizeof(c));    for (int i=1; i<=n; i++) AddT(in[i],1),AddT(out[i],-1);    m=Read();    for (int i=1; i<n+m; i++)    {        char ch=nc(); int x,y;        while (ch!='W'&&ch!='A') ch=nc();        if (ch=='W') x=Read(),printf("%d\n",GetT(in[x])-1);         else x=Read(),y=Read(),AddT(in[y],-1),AddT(out[y],1);    }    return 0;}

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