PAT甲级1135 Is It A Red-Black Tree？【dfs】

  1 #include<cstdio>
  2 #include<cstdlib>
  3 #include<map>
  4 #include<set>
  5 #include<iostream>
  6 #include<cstring>
  7 #include<algorithm>
  8 #include<vector>
  9 #include<cmath> 
 10 #include<stack>
 11 #include<queue>
 12 
 13 #define inf 0x7fffffff
 14 using namespace std;
 15 typedef long long LL;
 16 typedef pair<string, string> pr;
 17 
 18 int k, n;
 19 const int maxn = 35;
 20 struct node{
 21     int val;
 22     bool isred;
 23     int lchild, rchild;
 24 }nodes[maxn];
 25 
 26 int tot = 0;
 27 void addnode(int val)
 28 {
 29     if(val < 0){
 30         nodes[tot].isred = true;
 31         val = -val;
 32     }
 33     else{
 34         nodes[tot].isred = false;
 35     }
 36     nodes[tot].val = val;
 37     nodes[tot].lchild = nodes[tot].rchild = -1;
 38     
 39     int now = 0, prev = 0;
 40     while(now != -1){
 41         prev = now;
 42         if(val > nodes[now].val){
 43             now = nodes[now].rchild;
 44         }
 45         else{
 46             now = nodes[now].lchild;
 47         }
 48     }
 49     if(val > nodes[prev].val){
 50         nodes[prev].rchild = tot++;
 51     }
 52     else{
 53         nodes[prev].lchild = tot++;
 54     }
 55 }
 56 
 57 bool flag = true; 
 58 int dfs(int rt)
 59 {
 60     int l = nodes[rt].lchild, r = nodes[rt].rchild;
 61     int lres = 0, rres = 0;
 62     if(l != -1){
 63         if(dfs(l) == -1)return -1;
 64         lres += dfs(l);
 65     }
 66     if(r != -1){
 67         if(dfs(r) == -1)return -1;
 68         rres += dfs(r);
 69     }
 70     if(l == -1 && r == -1){
 71         return !nodes[rt].isred;
 72     }
 73     if(lres != rres){
 74         return -1;
 75     }
 76     if(nodes[rt].isred && (nodes[l].isred || nodes[r].isred)){
 77         return -1;
 78     }
 79     return lres + !nodes[rt].isred;
 80 }
 81  
 82 void printTree(int rt)
 83 {
 84     if(rt == -1)return;
 85     printf("%d ", nodes[rt].val);
 86     printTree(nodes[rt].lchild);
 87     printTree(nodes[rt].rchild);
 88 }
 89  
 90 int main()
 91 {
 92     scanf("%d", &k);
 93     while(k--){
 94         for(int i = 0; i <= tot; i++){
 95             nodes[tot].val = 0;
 96             nodes[tot].isred = 0;
 97             nodes[tot].lchild = nodes[tot].rchild = -1;
 98         }
 99         tot = 0;
100         flag = true;
101         scanf("%d", &n);
102         scanf("%d", &nodes[tot].val);
103         nodes[tot].isred = false;
104         nodes[tot].lchild = nodes[tot].rchild = -1;tot++;
105         for(int i = 1; i < n; i++){
106             int val;
107             scanf("%d", &val);
108             addnode(val);
109         }
110         
111         //printTree(0);
112         if(nodes[0].val < 0){
113             printf("No\n");
114         }
115         else{    
116             if(dfs(0) != -1){
117                 printf("Yes\n");
118             }
119             else{
120                 printf("No\n");
121             }
122         }
123     }
124     return 0;
125 }