'commit'

TangDou/LanQiaoBei/ZhongGaoJi/LanQiao15STEMA202401/7.cpp

@@ -0,0 +1,59 @@
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long LL;
+/*
+4
+1 2 3 4
+*/
+const int N = 110;
+struct Node {
+    int num;         // 啥数
+    int left, right; // 左侧是哪个节点，右侧是哪个节点
+} a[N];
+int st[N];
+int n;
+LL res;
+void dfs(int r, LL sum) { // u:本轮选择哪个靶子， r:剩余几次机会 sum:已经取得的累加和
+    if (r == 0) {
+        res = max(res, sum);
+        return;
+    }
+
+    for (int u = 1; u <= n; u++) {
+        if (!st[u]) {
+            int L = a[u].left, R = a[u].right;
+
+            st[u] = 1; // u号靶子被标识为已放倒
+            a[L].right = R;
+            a[R].left = L;
+
+            // 深搜
+            dfs(r - 1, sum + a[L].num * a[u].num * a[R].num);
+
+            // 回溯
+            a[L].right = u;
+            a[R].left = u;
+            st[u] = 0; // u被扶了起来
+        }
+    }
+}
+
+int main() {
+    cin >> n;
+    for (int i = 1; i <= n; i++) cin >> a[i].num;
+
+    // 左右哨兵
+    a[0].num = 1;
+    a[n + 1].num = 1;
+
+    // 预处理
+    for (int i = 1; i <= n; i++) {
+        a[i].left = a[i - 1].num;
+        a[i].right = a[i + 1].num;
+    }
+
+    dfs(n, 0);
+
+    cout << res << endl;
+    return 0;
+}