LCA
描述
加边，删边，动态求两点的lca
删边以后要恢复以前的跟，因为lca与树根有关，不能随意旋转树
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<algorithm> 5 using namespace std; 6 #define maxn 100020 7 8 int fa[maxn],child[maxn][2],rev[maxn]; 9 int n,m; 10 int stack[maxn],tops = -1; 11 12 inline bool isroot(int x){ 13 return (child[fa[x]][0] != x && child[fa[x]][1] != x); 14 } 15 inline void reverse(int x){ 16 rev[x] ^= 1; 17 swap(child[x][0],child[x][1]); 18 } 19 inline void pushdown(int x){ 20 if ( rev[x] ) { 21 if ( child[x][0] ) reverse(child[x][0]); 22 if ( child[x][1] ) reverse(child[x][1]); 23 rev[x] = 0; 24 } 25 } 26 inline void rotate(int x){ 27 int t = child[fa[x]][1] == x; 28 int y = fa[x] , z = child[x][1 - t]; 29 fa[x] = fa[y]; 30 if ( !isroot(y) ) child[fa[x]][child[fa[x]][1] == y] = x; 31 fa[y] = x; 32 child[x][1 - t] = y; 33 if ( z ){ 34 fa[z] = y; 35 } 36 child[y][t] = z; 37 } 38 inline void splay(int x){ 39 stack[++tops] = x; 40 for (int i = x ; !isroot(i) ; i = fa[i]) stack[++tops] = fa[i]; 41 while ( ~tops ) pushdown(stack[tops--]); 42 while ( !isroot(x) ){ 43 int y = fa[x] , z = fa[y]; 44 if ( (!((child[z][0] == y) ^ (child[y][0] == x))) && !isroot(y) ) rotate(y); 45 else rotate(x); 46 if ( isroot(x) ) break; 47 rotate(x); 48 } 49 } 50 inline int access(int x){ 51 int t = 0; 52 for (;x;x = fa[x]) 53 splay(x) , child[x][1] = t , t = x; 54 return t; 55 } 56 inline void makeroot(int x){ 57 access(x); 58 splay(x); 59 reverse(x); 60 } 61 inline void link(int x,int y){ 62 makeroot(y); 63 fa[y] = x; 64 } 65 inline int findroot(int x){ 66 access(x); 67 splay(x); 68 pushdown(x); 69 while ( child[x][0] ) x = child[x][0] , pushdown(x); 70 return x; 71 } 72 inline void cut(int x,int y){ 73 int R = findroot(x); 74 makeroot(y); 75 access(x); 76 splay(x); 77 child[x][0] = fa[y] = 0; 78 makeroot(R); 79 } 80 inline int getans(int x,int y){ 81 if ( findroot(x) != findroot(y) ) return -1; 82 access(x); 83 return access(y); 84 } 85 void print(){ 86 for (int i = 1 ; i <= n ; i++) cout<<i<<" fa "<<fa[i]<<" child "<<child[i][0]<<" "<<child[i][1]<<endl; 87 } 88 int main(){ 89 freopen("lca.in","r",stdin); 90 freopen("lca.out","w",stdout); 91 scanf("%d %d",&n,&m); 92 for (int i = 1 ; i <= m ; i++){ 93 int t,x,y; 94 scanf("%d %d %d",&t,&x,&y); 95 if ( t == 1 ) link(x,y); 96 else if ( t == 2 ){ 97 if ( fa[x] == y ) cut(x,y); 98 else cut(y,x); 99 } 100 else printf("%d ",getans(x,y)); 101 // cout<<i<<endl; 102 // print(); 103 } 104 return 0; 105 }