feat : reverse-bits

Author: ekgns33

reverse-bits/ekgns33.java

@@ -0,0 +1,39 @@
+/*
+input : 32 bit unsigned integer n
+output : unsigned integer representation of reversed bit
+constraint :
+1) input is always 32 bit unsigned integer
+2) implementation should not be affected by programming language
+
+solution 1)
+
+get unsigned integer bit representation
+
+build string s O(n)
+reverse O(n)
+get integer O(n)
+
+tc : O(n) sc : O(n)
+
+solution 2) one loop
+
+nth bit indicates (1<<n) if reverse (1<< (32 - n))
+add up in one loop
+return 
+
+tc : O(n), sc:  O(1)
+
+ */
+public class Solution {
+  // you need treat n as an unsigned value
+  static final int LENGTH = 32;
+  public int reverseBits(int n) {
+    int answer = 0;
+    for(int i = 0; i < LENGTH; i++) {
+      if(((1<<i) & n) != 0) {
+        answer += (1 << (LENGTH -  i - 1));
+      }
+    }
+    return answer;
+  }
+}