P2157 [SDOI2009] 学校食堂

https://www.luogu.com.cn/record/77474202

Luogu/P2157/P2157.cpp

@@ -0,0 +1,68 @@
+#include <iostream>
+#include <cstring>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1005;
+const int INF = 0x3f3f3f3f;
+
+int c, n, f[N][1 << 8][20];
+std::pair<int, int> a[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> c;
+
+    while (c--) {
+        memset(f, 0x3f, sizeof(f));
+
+        cin >> n;
+
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i].first >> a[i].second;
+        }
+
+        f[1][0][7] = 0;
+        for (int i = 1; i <= n; i++) {
+            for (int j = 0; j < 1 << 8; j++) {
+                for (int k = -8; k <= 7; k++) {
+                    if (f[i][j][k + 8] != INF) {
+                        if (j & 1) {  // 当前同学吃了，无需考虑后方
+                            f[i + 1][j >> 1][k + 7] = std::min(f[i + 1][j >> 1][k + 7], f[i][j][k + 8]);
+                        } else {
+                            int t = INF;
+
+                            for (int l = 0; l <= 7; l++) {
+                                if (j & 1 << l) continue;
+                                if (i + l > t) break;
+
+                                if (i + l <= n) t = std::min(t, i + l + a[i + l].second);
+                                else t = std::min(t, i + l);
+
+                                if (i + k) {
+                                    int x = i + k <= n ? a[i + k].first : 0,
+                                        y = i + l <= n ? a[i + l].first : 0;
+                                    f[i][j | 1 << l][l + 8] = std::min(f[i][j | 1 << l][l + 8], f[i][j][k + 8] + (x ^ y));
+                                } else {
+                                    f[i][j | 1 << l][l + 8] = std::min(f[i][j | 1 << l][l + 8], f[i][j][k + 8]);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        int ans = INF;
+        for (int i = 0; i <= 8; i++) {
+            ans = std::min(ans, f[n + 1][0][i]);
+        }
+        cout << ans << endl;
+    }
+
+    return 0;
+}