[BOJ 1068] 트리

src/week2/BOJ1068/BOJ1068_V1.cpp

@@ -0,0 +1,55 @@
+#include <bits/stdc++.h>
+using namespace std;
+int target;
+int N;
+vector<vector<int>> tree;
+int cnt = 0;
+void dfs(int num) {
+    if (tree[num].size() == 0) {
+        cnt++;
+        return;
+    }
+
+    for (int i : tree[num]) {
+        dfs(i);
+    }
+}
+
+int main() {
+
+    cin >> N;
+    for (int i = 0; i < N; i++) {
+        tree.push_back(vector<int>());
+        int num;
+        cin >> num;
+        if (num == -1) continue;
+        tree[num].push_back(i);
+    }
+
+    cin >> target;
+    if (target == 0) {
+        cout << 0;
+        return 0;
+    }
+
+    tree[target].clear();
+    int num = 0;
+    int flag = true;
+    while(flag) {
+        if (num == tree.size())
+            break;
+        for (int i=0; i<tree[num].size(); i++) {
+            if (tree[num][i] == target) {
+                flag = false;
+                tree[num].erase(tree[num].begin() + i);
+                break;
+            }
+        }
+        num++;
+    }
+
+    dfs(0);
+    cout << cnt;
+
+    return 0;
+}

src/week2/BOJ1068/BOJ1068_V2.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+using namespace std;
+int target;
+int N;
+vector<vector<int>> tree;
+int dfs(int num) {
+    int ret = 0;
+    int child = 0;
+    for (int i : tree[num]) {
+        if (i == target) continue;
+        ret += dfs(i);
+        child++;
+    }
+
+    if (child == 0)
+        return 1;
+
+    return ret;
+}
+
+int main() {
+
+    cin >> N;
+    for (int i = 0; i < N; i++) {
+        tree.push_back(vector<int>());
+        int num;
+        cin >> num;
+        if (num == -1) continue;
+        tree[num].push_back(i);
+    }
+
+    cin >> target;
+    if (target == 0) {
+        cout << 0;
+        return 0;
+    }
+
+
+    cout << dfs(0);
+
+    return 0;
+}