new 1 bit copy from jdk

tg123 · tg123 · commit bb909aa57f2f · 2015-03-10T12:33:10.000+08:00
diff --git a/number-of-1-bits/README.md b/number-of-1-bits/README.md
diff --git a/number-of-1-bits/Solution.java b/number-of-1-bits/Solution.java
@@ -0,0 +1,27 @@
+public class Solution {
+  // copy from JDK Integer.bitCount
+  /**
+  * Returns the number of one-bits in the two's complement binary
+  * representation of the specified {@code int} value.  This function is
+  * sometimes referred to as the <i>population count</i>.
+  *
+  * @param i the value whose bits are to be counted
+  * @return the number of one-bits in the two's complement binary
+  *     representation of the specified {@code int} value.
+  * @since 1.5
+  */
+  public static int bitCount(int i) {
+    // HD, Figure 5-2
+    i = i - ((i >>> 1) & 0x55555555);
+    i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
+    i = (i + (i >>> 4)) & 0x0f0f0f0f;
+    i = i + (i >>> 8);
+    i = i + (i >>> 16);
+    return i & 0x3f;
+  }
+
+  // you need to treat n as an unsigned value
+  public int hammingWeight(int n) {
+    return bitCount(n);
+  }
+}
diff --git a/number-of-1-bits/index.md b/number-of-1-bits/index.md
@@ -0,0 +1,9 @@
+---
+layout: solution
+title: Number of 1 Bits
+date: 2015-03-10 12:29:58+08:00
+leetcode_id: 191
+---
+{% assign leetcode_name = {{page.path | remove: '/index.md'}}  %}
+{% assign leetcode_readme = {{leetcode_name | append: '/README.md' | prepend: '_root/' }}  %}
+{% include {{leetcode_readme}} %}
