boj 4442 빌보의 생일

Author: emost22

세그먼트 트리/4442.cpp

@@ -0,0 +1,72 @@
+#include <iostream>
+#include <unordered_map>
+#include <string>
+#include <cstring>
+#define MAX 100001
+using namespace std;
+typedef long long ll;
+
+unordered_map<string, int> m;
+int idxList[MAX];
+ll tree[MAX << 2];
+int N;
+
+void init() {
+	m.clear();
+	memset(tree, 0, sizeof(tree));
+}
+
+ll update(int node, int l, int r, int idx, int diff) {
+	if (idx < l || r < idx) return tree[node];
+	if (l == r) return ++tree[node];
+
+	int m = (l + r) >> 1;
+	return tree[node] = update(node << 1, l, m, idx, diff) + update((node << 1) + 1, m + 1, r, idx, diff);
+}
+
+ll query(int node, int l, int r, int s, int e) {
+	if (l > e || r < s) return 0LL;
+	if (s <= l && r <= e) return tree[node];
+
+	int m = (l + r) >> 1;
+	return query(node << 1, l, m, s, e) + query((node << 1) + 1, m + 1, r, s, e);
+}
+
+void func() {
+	ll ret = 0LL;
+	for (int i = 0; i < N; i++) {
+		ret += query(1, 1, N, idxList[i] + 1, N);
+		update(1, 1, N, idxList[i], 1);
+	}
+	cout << ret << '\n';
+}
+
+void input() {
+	cin >> N;
+	if (!N) exit(0);
+	
+	string str;
+	int cnt = 0;
+	for (int i = 0; i < N; i++) {
+		cin >> str;
+		m[str] = ++cnt;
+	}
+
+	for (int i = 0; i < N; i++) {
+		cin >> str;
+		idxList[i] = m[str];
+	}
+}
+
+int main() {
+	cin.tie(nullptr); cout.tie(nullptr);
+	ios::sync_with_stdio(false);
+
+	while (1) {
+		input();
+		func();
+		init();
+	}
+
+	return 0;
+}