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FZOI/四色问题.cpp

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+#include <iostream>
+#include <cstring>
+using namespace std;
+
+const int MAXN = 8;
+int n;
+int arr[MAXN][MAXN];
+int color[MAXN];
+int ans;
+
+bool f(int v, int c)
+{
+    for (int i = 0; i < n; i++)
+    {
+        if (arr[v][i] && color[i] == c)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+void dfs(int v)
+{
+    if (v == n)
+    {
+        ans++;
+        return;
+    }
+    for (int c = 1; c <= 4; c++)
+    {
+        if (f(v, c))
+        {
+            color[v] = c;
+            dfs(v + 1);
+            color[v] = 0;
+        }
+    }
+}
+
+int main()
+{
+    cin >> n;
+    for (int i = 0; i < n; i++)
+    {
+        for (int j = 0; j < n; j++)
+        {
+            cin >> arr[i][j];
+        }
+    }
+    memset(color, 0, sizeof(color));
+    ans = 0;
+    dfs(0);
+    cout << ans << endl;
+    return 0;
+}