P3105 [USACO14OPEN]Fair Photography S

https://www.luogu.com.cn/record/83996634

Luogu/P3105/P3105.cpp

@@ -0,0 +1,47 @@
+#include <iostream>
+#include <algorithm>
+#include <cstring>
+#include <utility>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, f[N << 1], ans;
+std::pair<int, char> cows[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    memset(f, 0x3f, sizeof(f));
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> cows[i].first >> cows[i].second;
+    }
+
+    std::sort(cows + 1, cows + 1 + n);
+
+    f[n] = cows[1].first;
+    for (int i = 2, x = n; i <= n; i++) {
+        x += cows[i - 1].second == 'W' ? -1 : 1;
+        f[x] = std::min(f[x], cows[i].first);
+    }
+
+    for (int i = n << 1; i; i--) {
+        f[i] = std::min(f[i], f[i + 2]);
+    }
+
+    for (int i = 1, x = n; i <= n; i++) {
+        x += cows[i].second == 'W' ? -1 : 1;
+        ans = std::max(ans, cows[i].first - f[x]);
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}