add solution of problem 228: summary ranges

Author: ppulse

SummaryRanges228/README.md

@@ -0,0 +1,3 @@
+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"]`.

SummaryRanges228/Solution.java

@@ -0,0 +1,34 @@
+public class Solution {
+    public List<String> summaryRanges(int[] nums) {
+        List<String> result = new ArrayList<String>();
+        if (nums == null)
+            return result;
+        
+        int idx = 0;
+        while (idx < nums.length) {
+            int startIdx = idx;
+            int endIdx = idx;
+            
+            while (idx < nums.length - 1 && nums[idx] + 1 == nums[idx + 1]) {
+                endIdx++;
+                idx++;
+            }
+            
+            String s;
+            if (endIdx > startIdx) {
+                s = "" + nums[startIdx] + "->" + nums[endIdx];
+            } else {
+                s = "" + nums[startIdx];
+            }
+            
+            result.add(s);
+            
+            if (idx == nums.length - 1)
+                break;
+            else
+                idx++;
+        }
+        
+        return result;
+    }
+}