2170. 선 긋기 - 좌표 압축

baekjoon/cpp/c++/2170.cpp

@@ -0,0 +1,62 @@
+#include <bits/stdc++.h>
+
+using pii = std::pair<int, int>;
+
+int n;
+std::vector<pii> points;
+
+void getinput()
+{
+    std::cin >> n;
+    for (int i = 0; i < n; i++)
+    {
+        int x, y;
+        std::cin >> x >> y;
+        points.emplace_back(x, y);
+    }
+}
+
+int solve()
+{
+    // O(N)
+    std::vector<int> coords;
+    for (auto &[x, y] : points)
+    {
+        coords.push_back(x);
+        coords.push_back(y);
+    }
+    // O(NlogN)
+    std::sort(coords.begin(), coords.end());
+    auto it = std::unique(coords.begin(), coords.end());
+
+    int zip_coord_size = coords.size();
+    std::vector<int> start(zip_coord_size, 0), finish(zip_coord_size, 0);
+    for (auto &[x, y] : points)
+    {
+        auto xp = std::lower_bound(coords.begin(), it, x);
+        auto yp = std::lower_bound(coords.begin(), it, y);
+        start[xp - coords.begin()]++;
+        finish[yp - coords.begin()]++;
+    }
+
+    // O(N)
+    int ans = 0, count = start[0];
+    for (int i = 1; i < zip_coord_size; i++)
+    {
+        if (count > 0)
+        {
+            ans += coords[i] - coords[i - 1];
+        }
+        count = count + start[i] - finish[i];
+    }
+    return ans;
+}
+
+int main()
+{
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(0);
+
+    getinput();
+    std::cout << solve() << '\n';
+}