pipioj 1265: 最近公共祖先
http://www.pipioj.online/problem.php?id=1265
1 #define bug(x) cout<<#x<<" is "<<x<<endl 2 #define IO std::ios::sync_with_stdio(0) 3 #define ull unsigned long long 4 #include <bits/stdc++.h> 5 #define iter ::iterator 6 #define pa pair<int,ll> 7 #define pp pair<int,pa> 8 using namespace std; 9 #define ll long long 10 #define mk make_pair 11 #define pb push_back 12 #define se second 13 #define fi first 14 #define ls o<<1 15 #define rs o<<1|1 16 ll mod=998244353; 17 const int N=2e5+5; 18 19 vector<int>g[N]; 20 21 int a[N],b[N],c[N]; 22 int l[N],r[N],fa[N]; 23 24 int tot=1,cnt=0; 25 26 void dfs(int x){ 27 if(tot>cnt)return; 28 if(x==-1){ 29 return; 30 } 31 32 l[x]=a[++tot]; 33 fa[a[tot]]=x; 34 dfs(a[tot]); 35 r[x]=a[++tot]; 36 fa[a[tot]]=x; 37 dfs(a[tot]); 38 } 39 int main(){ 47 IO; 48 int x; 49 while(cin>>x){ 50 a[++cnt]=x; 51 } 52 fa[a[1]]=-1; 53 dfs(a[1]); 54 int y,n1=0,n2=0; 55 y=a[cnt-1]; 56 while(y!=-1){ 57 b[++n1]=y; 58 y=fa[y]; 59 } 60 y=a[cnt]; 61 while(y!=-1){ 62 c[++n2]=y; 63 y=fa[y]; 64 } 65 if(n1>n2){ 66 for(int i=1;i<=n2;i++){ 67 if(b[i+n1-n2]==c[i]){ 68 cout<<c[i]<<endl; 69 break; 70 } 71 } 72 } 73 else{ 74 for(int i=1;i<=n1;i++){ 75 if(b[i]==c[i+n2-n1]){ 76 cout<<b[i]<<endl; 77 break; 78 } 79 } 80 } 81 /*for(int i=1;i<=8;i++){ 82 printf("i=%d: %d %d\n",i,l[i],r[i]); 83 }*/ 84 85 86 }
非递归版
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef int ElemType; 4 5 typedef struct Node{ 6 ElemType data; 7 Node* lson; 8 Node* rson; 9 Node(ElemType data, Node* lson, Node* rson) { 10 this->data = data; 11 this->lson = lson; 12 this->rson = rson; 13 } 14 }*Tree; 15 16 stack<Tree>s,s1,s2; 17 18 Tree build(){ 19 int x; 20 scanf("%d",&x); 21 if(x==-1)return NULL; 22 Tree T=(Tree)malloc(sizeof(Node)); 23 T->data=x; 24 T->lson=build(); 25 T->rson=build(); 26 return T; 27 } 28 29 void preorder(Tree T){ 30 if(T){ 31 printf("%d ",T->data); 32 preorder(T->lson); 33 preorder(T->rson); 34 } 35 36 } 37 38 int get_ancester(Tree T,int x,int y){ 39 Tree p=T; 40 Tree r=NULL; 41 while(p||!s.empty()){ 42 if(p){ 43 s.push(p); 44 p=p->lson; 45 } 46 else{ 47 p=s.top(); 48 if(p->data==x)s1=s; 49 if(p->data==y)s2=s; 50 if(!s1.empty()&&!s2.empty())break; 51 if(p->rson&&p->rson!=r)p=p->rson; 52 else{ 53 s.pop(); 54 r=p; 55 p=NULL; 56 } 57 } 58 } 59 if(s1.empty()||s2.empty())return -1; 60 int n=s1.size(),m=s2.size(); 61 //int t=n<m?n:m; 62 if(n<m)while(m>n)m--,s2.pop(); 63 else while(n>m)n--,s1.pop(); 64 while(!s1.empty()){ 65 if(s1.top()==s2.top())break; 66 s1.pop(); 67 s2.pop(); 68 } 69 printf("%d\n",s1.top()->data); 70 /*while(!s1.empty()){ 71 printf("%d ",s1.top()->data); 72 s1.pop(); 73 }*/ 74 return 1; 75 76 } 77 78 79 int main(){ 80 /*Node* v7 = new Node(7, NULL, NULL); 81 Node* v1 = new Node(1, NULL, NULL); 82 Node* v3 = new Node(3, NULL, NULL); 83 Node* v2 = new Node(2, v1, v3); 84 Node* v5 = new Node(5, NULL, NULL); 85 Node* v6 = new Node(6, v5, v7); 86 Node* v4 = new Node(4, v2, v6);*/ 87 88 //Tree T=v4; 89 //get_ancester(T,1,8); 90 Tree T; 91 T=build(); 92 int x,y; 93 scanf("%d%d",&x,&y); 94 get_ancester(T,x,y); 95 //preorder(T); 96 97 }
