PAT 甲級 1135 Is It A Red-Black Tree (30 分) 指針建樹+dfs

馬一下，，，這個題真滴蠢

ps：紅黑樹的葉子結點省略了，全是NULL，先序遍歷的時候不會輸出

#include<bits/stdc++.h>
#include<cstring>
#define FI first
#define SE second

using namespace std;
typedef long long ll;
typedef pair<string, string> P;
const int maxn = 100 + 7;
int n;
set<int> st;
int arr[maxn];
struct node {
    int v;
    node *l, *r;
};
node *build(node *root, int v) {
    if(root == NULL) {
        root = new node();
        root->v = v;
        root->l = root->r = NULL;
    }
    else if(abs(v) <= abs(root->v)) {
        root->l = build(root->l, v);
    }
    else {
        root->r = build(root->r, v);
    }
    return root;
}
bool judge1(node *root) {
    if (root == NULL) return true;
    if (root->v < 0) {
        if (root->l != NULL && root->l->v < 0) return false;
        if (root->r != NULL && root->r->v < 0) return false;
    }
    return judge1(root->l) && judge1(root->r);
}
void dfs(node *root, int cnt) {
    if(root == NULL) {
        st.insert(cnt);
        return;
    }
    int t = 0;
    if(root->v > 0) t = 1;
    dfs(root->l, cnt+t);
    dfs(root->r, cnt+t);
}
bool judge2(node *root) {
    if (root == NULL) return true;
    st.clear();
    dfs(root, 0);
    if(st.size() != 1) return false;
    return judge2(root->l) && judge2(root->r);
}
int main() {
    int T; cin >> T;
    while(T--) {
        cin >> n;
        node *root = NULL;
        for(int i = 0; i < n; ++i) {
            cin >> arr[i];
            root = build(root, arr[i]);
        }
        if(arr[0] < 0 || judge1(root) == false || judge2(root) == false) {
            puts("No");
        }
        else {
            puts("Yes");
        }
    }

    return 0;
}