Merge pull request #1747 from AlgorithmWithGod/khj20006

[20251228] BOJ / P5 / 인경호의 나무 / 권혁준

Author: ShinHeeEul

khj20006/202512/28 BOJ P5 인경호의 나무.md

@@ -0,0 +1,47 @@
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+using ll = long long;
+
+const ll MOD = 1e9 + 7;
+
+int N, M;
+int a[1001]{}, l[1001]{}, r[1001]{};
+ll c[2001][1001]{};
+
+vector<int> res;
+
+void inorder(int n) {
+    if(l[n] != -1) inorder(l[n]);
+    res.push_back(a[n]);
+    if(r[n] != -1) inorder(r[n]);
+}
+
+int main() {
+    cin.tie(0)->sync_with_stdio(0);
+
+    for(int k=1;k<=2000;k++) {
+        c[k][1] = k;
+        for(int i=2;i<=min(k,1000);i++) c[k][i] = (c[k-1][i-1] + c[k-1][i]) % MOD;
+    }
+
+    cin>>N>>M;
+    for(int i=1;i<=N;i++) cin>>a[i]>>l[i]>>r[i];
+
+    inorder(1);
+    res.push_back(M+1);
+    ll ans = 1, prev = 0;
+    for(int i=0;i<res.size();i++) {
+        if(res[i] == -1) {
+            int cnt = 0;
+            while(i<res.size() && res[i] == -1) i++, cnt++;
+            if(res[i] <= prev) return cout<<0,0;
+            if(cnt > res[i] - prev - 1) return cout<<0,0;
+            ans = (ans * c[res[i]-prev-1][cnt]) % MOD;
+        }
+        prev = res[i];
+    }
+    cout<<ans;
+
+}
+```