[20251129] BOJ / P4 / 츠바메가에시 / 권혁준

khj20006/202511/29 BOJ P4 츠바메가에시.md

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+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+struct SegmentTree {
+	vector<pair<int, int>> tree;
+
+	pair<int, int> mrg(pair<int, int> &a, pair<int, int> &b) {
+		int mx1 = 0, mx2 = 0;
+		mx1 = max(a.first, b.first);
+		if (mx1 == a.first) mx2 = max(a.second, b.first);
+		else mx2 = max(a.first, b.second);
+		return { mx1, mx2 };
+	}
+public:
+	SegmentTree(int sz) {
+		tree.resize(sz * 4);
+	}
+
+	void upt(int s, int e, int i, int v, int n) {
+		if (s == e) {
+			tree[n].first += v;
+			return;
+		}
+		int m = (s + e) >> 1;
+		if (i <= m) upt(s, m, i, v, n << 1);
+		else upt(m + 1, e, i, v, n << 1 | 1);
+		tree[n] = mrg(tree[n << 1], tree[n << 1 | 1]);
+	}
+};
+
+int N;
+SegmentTree* segX = new SegmentTree(1000001);
+SegmentTree* segY = new SegmentTree(1000001);
+vector<pair<int, int>> X[1000001];
+vector<pair<int, int>> Y[1000001];
+
+int main() {
+	cin.tie(0)->sync_with_stdio(0);
+
+	cin >> N;
+	for (int i = 0, x, y, v; i < N; i++) {
+		cin >> x >> y >> v;
+		X[x].emplace_back(y, v);
+		Y[y].emplace_back(x, v);
+		segX->upt(0, 1000000, x, v, 1);
+		segY->upt(0, 1000000, y, v, 1);
+	}
+
+	int ans = 0;
+	int xmx1 = 0, xmx2 = 0, xmx3 = 0;
+	for (int x = 0; x <= 1000000; x++) {
+		int sum = 0;
+		for (auto [y, v] : X[x]) {
+			segY->upt(0, 1000000, y, -v, 1);
+			sum += v;
+		}
+		auto [a, b] = segY->tree[1];
+		ans = max(ans, sum + a + b);
+		for (auto [y, v] : X[x]) {
+			segY->upt(0, 1000000, y, v, 1);
+		}
+		if (sum > xmx1) xmx3 = xmx2, xmx2 = xmx1, xmx1 = sum;
+		else if (sum > xmx2) xmx3 = xmx2, xmx2 = sum;
+		else if (sum > xmx3) xmx3 = sum;
+	}
+	ans = max(ans, xmx1 + xmx2 + xmx3);
+
+	int ymx1 = 0, ymx2 = 0, ymx3 = 0;
+	for (int y = 0; y <= 1000000; y++) {
+		int sum = 0;
+		for (auto [x, v] : Y[y]) {
+			segX->upt(0, 1000000, x, -v, 1);
+			sum += v;
+		}
+		auto [a, b] = segX->tree[1];
+		ans = max(ans, sum + a + b);
+		for (auto [x, v] : Y[y]) {
+			segX->upt(0, 1000000, x, v, 1);
+		}
+		if (sum > ymx1) ymx3 = ymx2, ymx2 = ymx1, ymx1 = sum;
+		else if (sum > ymx2) ymx3 = ymx2, ymx2 = sum;
+		else if (sum > ymx3) ymx3 = sum;
+	}
+	ans = max(ans, ymx1 + ymx2 + ymx3);
+
+	cout << ans;
+
+}
+```