LeetCode Day2

Power of Two

 /**
  * LeetCode: Power of Two
  * Given an integer, write a function to determine if it is a power of two.
  *
  * @author LuoPeng
  * @time 2015.8.3
  *
  */
 public class PowerOfTwo {

     public boolean isPowerOfTwo(int n) {

         boolean result = false;
         if ( n == 1) {
             result = true;
         } else if ( n > 1) {
             while ( n % 2 == 0) {
                 n = n/2;
             }
             result = (n==1)?true:false;
         }
         return result;
     }

 }

Summary Ranges

 /**
  * LeetCode: Summary Ranges
  * Given a sorted integer array without duplicates, return the summary of its ranges.
  * For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].
  *
  * If the next value is equal to the current value+1, then the next value should be merged together.
  * Input:[0, 1, 5, 7, 8]; output:["0->1", "5", "7->8"
  * Input:[3, 5, 6, 7, 9]; output:["3", "5->7", "9"]
  *
  * @author LuoPeng
  * @time 2015.8.4
  *
  */
 public class SummaryRanges {

     /**
      *
      * @param nums
      * @return
      */
     public List<String> summaryRanges(int[] nums) {

         if ( nums == null) {return null;}

         List<String> result = new ArrayList<String>();
         if ( nums.length != 0) {
             String temp = null;
             int length = nums.length;
             int start = 0;
             for ( int i = 1; i < length; i++) {
                 if ( nums[i] - nums[i-1] != 1) {
                     if ( i == start+1) {
                         // the value should be itself
                         temp = "" + nums[start];
                     }  else {
                         temp = nums[start] + "->" + nums[i-1];
                     }
                     result.add(temp);
                     start = i;
                 }
             }

             // the last element
             if ( length == start+1) {
                 temp = "" + nums[start];
             }  else {
                 temp = nums[start] + "->" + nums[length-1];
             }
             result.add(temp);
         }

         return result;

     }

 }