'commit'

TangDou/LuoGuBook/20_1_9_3.cpp

@@ -0,0 +1,17 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+int cnt;
+
+int main() {
+    int n = 10;
+    int u = 1 << n;
+    for (int s = 0; s <= u - 1; s++) {
+        int q = 4;
+        for (int i = n - 1; i >= 0; i--)
+            if (s & (1 << i)) q--;
+            if (!q)cnt++;
+    }
+    cout << cnt << endl;
+    return 0;
+}