UVA307 小木棍 Sticks

https://www.luogu.com.cn/record/85779684

Luogu/UVA307/UVA307.cpp

@@ -0,0 +1,89 @@
+#include <iostream>
+#include <algorithm>
+#include <functional>
+#include <numeric>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 70;
+
+int n, m, l, a[N], next[N];
+bool flag, vis[N];
+
+void dfs(int now, int last, int rest) {
+    if (!rest) {
+        if (now == m) {
+            flag = true;
+
+            return;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (!vis[i]) {
+                vis[i] = true;
+                dfs(now + 1, i, l - a[i]);
+                if (flag) return;
+                vis[i] = false;
+
+                break;
+            }
+        }
+    }
+
+    int p = std::lower_bound(a + last + 1, a + n + 1, rest, std::greater<int>()) - a;
+
+    for (int i = p; i <= n; i++) {
+        if (!vis[i]) {
+            vis[i] = true;
+            dfs(now, i, rest - a[i]);
+            vis[i] = false;
+
+            if (flag || rest == a[i] || rest == l) return;
+            i = next[i];
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    while (cin >> n, n) {
+        flag = false;
+        std::fill_n(a, N, 0);
+        std::fill_n(next, N, 0);
+        std::fill_n(vis, N, false);
+        vis[1] = true;
+
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i];
+        }
+
+        int sum = std::accumulate(a + 1, a + 1 + n, 0);
+
+        std::sort(a + 1, a + 1 + n, std::greater<int>());
+
+        for (int i = n; i; i--) {
+            next[i] = a[i] == a[i + 1] ? next[i + 1] : i;
+        }
+
+        for (l = a[1]; l <= sum / 2; l++) {
+            if (sum % l) continue;
+
+            m = sum / l;
+            dfs(1, 1, l - a[1]);
+
+            if (flag) {
+                cout << l << endl;
+
+                break;
+            }
+        }
+
+        if (!flag) cout << sum << endl;
+    }
+
+    return 0;
+}