delete pics to save space

2.818.cpp

@@ -0,0 +1,85 @@
+#include<cstdio>
+#include<cstring>
+#include<algorithm>
+using namespace std;
+const int maxn = 15 + 5, INF = 10;
+int n, x, y, ans, num, C;
+int m[maxn][maxn], v[maxn];
+bool two(int s)
+{
+    for (int i = 0; i < n; ++i)
+    {
+        int cnt = 0;
+        for (int j = 0; j < n; ++j)
+            if (m[i][j] && !(s & (1 << i)) && !(s & (1 << j)))
+            {
+                ++cnt;
+                if (cnt == 3)
+                    return true;
+            }
+    }
+    return false;
+}
+bool DFS(int x, int f, int s)
+{
+    v[x] = 1;
+    for (int i = 0; i < n; ++i)
+        if (m[x][i] && !(s & (1 << i)))
+        {
+            if (!v[i])
+            {
+                if (DFS(i, x, s))
+                    return true;
+            }
+            else if (i != f)
+                return true;
+        }
+    return false;
+}
+bool circle(int s)
+{
+    memset(v, 0, sizeof(v));
+    for (int i = 0; i < n; ++i)
+        if (!v[i] && !(s & (1 << i)))
+        {
+            if (DFS(i, -1, s))
+                return true;
+            ++num;
+        }
+    return false;
+}
+int calc(int s)
+{
+    int res = 0;
+    for (int i = 0; i < n; ++i)
+    {
+        if (s & 1)
+            ++res;
+        s >>= 1;
+    }
+    return res;
+}
+int main()
+{
+    while (scanf("%d", &n)==1&&n)
+    {
+        ans = n;
+        memset(m, 0, sizeof(m));
+        while (scanf("%d%d", &x, &y), x != -1 && y != -1)
+        {
+            m[x - 1][y - 1] = 1;
+            m[y - 1][x - 1] = 1;
+        }
+        for (int i = 0; i < (1 << n); ++i)
+        {
+            num = 0;
+            if (two(i) || circle(i))
+                continue;
+            int tmp = calc(i);
+            if (num - 1 <= tmp)
+                ans = min(ans, tmp);
+        }
+        printf("Set %d: Minimum links to open is %d\n", ++C, ans);
+    }
+    return 0;
+}