git reimport

archive/2017.03/2017.03.05 - unsorted/D.java

@@ -0,0 +1,45 @@
+package chelper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import io.InputReader;
+import io.OutputWriter;
+
+public class D {
+  public void solve(int testNumber, InputReader in, OutputWriter out) {
+    int n = in.nextInt();
+    int k = in.nextInt();
+    int M = 1 << 16;
+    int[] a = new int[M];
+    for (int i = 0; i < n; i++) {
+      int x = in.nextInt();
+      a[x]++;
+    }
+
+    List<Integer> masks = new ArrayList<>();
+    for (int i = 0; i < M; i++) {
+      if (Integer.bitCount(i) == k) {
+        masks.add(i);
+      }
+    }
+
+    long answer = 0;
+    for (int i = 0; i < M; i++) {
+      if (a[i] == 0) {
+        continue;
+      }
+      for (int mask : masks) {
+        if ((i ^ mask) < i) {
+          answer += a[i] * a[i ^ mask];
+        }
+        if ((i ^ mask) == i) {
+          answer += a[i] * (a[i] - 1) / 2;
+        }
+      }
+    }
+
+    out.println(answer);
+  }
+
+}