Add C# solutions

README.md

@@ -20,6 +20,10 @@ Solutions in various programming languages are provided. Enjoy it.
 11. [Maximum Product Subarray](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/11-Maximum-Product-Subarray)
 12. [Combination Sum III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/12-Combination-Sum-III)
 13. [Insert Interval](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/13-Insert-Interval)
+14. [House Robber](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/14-House-Robber)
+15. [Length of Last Word](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/15-Length-of-Last-Word)
+16. [Maximum XOR of Two Numbers in an Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/16-Maximum-XOR-of-Two-Numbers-in-an-Array)
+17. [Robot Bounded In Circle](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/17-Robot-Bounded-In-Circle)
 
 ## August LeetCoding Challenge
 Click [here](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge/) for problem descriptions.

September-LeetCoding-Challenge/14-House-Robber/House-Robber.cs

@@ -0,0 +1,12 @@
+public class Solution {
+    public int Rob(int[] nums) {
+        if(nums.Length == 0) return 0;
+
+        var dp = new int[nums.Length+1];
+        dp[1] = nums[0];
+        for(int i=1; i<nums.Length; i++){
+            dp[i+1] = Math.Max(dp[i], dp[i-1] + nums[i]);
+        }
+        return dp[nums.Length];
+    }
+}

September-LeetCoding-Challenge/15-Length-of-Last-Word/Length-of-Last-Word.cs

@@ -0,0 +1,74 @@
+public class Solution {
+
+    //Solution 1
+    public class Solution {
+    public int LengthOfLastWord(string s) {
+        if(s.Length == 0) return 0;
+
+        var l = s.Split(' ').ToList();
+        var i = l.Count - 1;
+        while(i >= 0){
+            if(l[i] == ""){
+                i--;
+            }
+            else{
+                return l[i].Length;
+            }
+        }
+
+        return 0;
+    }
+}
+
+
+    //Solution 2
+    public int LengthOfLastWord(string s)
+        {
+            if (s.Length == 0) return 0;
+
+            int beginPosition = 0;
+            int endPosition = 0;
+            bool hasWord = false;
+            bool hasSpaceBeforeLastWord = false;
+
+            //Start by the end of string
+            for (int i = s.Length - 1; i >= 0; i--)
+            {
+                if (s[i] == ' ' && !hasWord)
+                {
+                    //This condition improves performance
+                    continue;
+                }
+                else if (s[i] != ' ' && !hasWord)
+                {
+                    hasWord = true;
+                    endPosition = i;
+                    continue;
+                }
+                else if (s[i] == ' ' && hasWord)
+                {
+                    beginPosition = i;
+                    hasSpaceBeforeLastWord = true;
+                    break;
+                }
+            }
+
+            //One word case
+            if (endPosition - beginPosition == 0 && hasWord)
+                return 1;
+
+            //No words case
+            if (endPosition - beginPosition == 0 && !hasWord)
+                return 0;
+
+            //Has word and has spaces before last words
+            if (endPosition - beginPosition != 0 && hasWord && hasSpaceBeforeLastWord)
+                return endPosition - beginPosition;
+
+            //Has word and has no space before last words
+            if (endPosition - beginPosition != 0 && hasWord && !hasSpaceBeforeLastWord)
+                return endPosition - beginPosition + 1;
+
+            return 0;
+        }
+}

September-LeetCoding-Challenge/16-Maximum-XOR-of-Two-Numbers-in-an-Array/Maximum-XOR-of-Two-Numbers-in-an-Array.cs

@@ -0,0 +1,22 @@
+public class Solution {
+    public int FindMaximumXOR(int[] nums) {
+        int max = 0, mask=0;
+        for(int i=31; i>=0; i--){
+            mask |= (1 << i);
+
+            var hs = new HashSet<int>();
+            foreach(int num in nums){
+                hs.Add(num & mask);
+            }
+
+            int tmp = max | (1 << i);
+            foreach(int prefix in hs){
+                if(hs.Contains(tmp ^ prefix)){
+                    max = tmp;
+                    break;
+                }
+            }
+        }
+        return max;
+    }
+}

September-LeetCoding-Challenge/17-Robot-Bounded-In-Circle/Robot-Bounded-In-Circle.cs

@@ -0,0 +1,21 @@
+public class Solution {
+    public bool IsRobotBounded(string instructions) {
+        int x = 0;
+        int y = 0;
+        var dirs = new int[4][]{new int[]{0,1}, new int[]{1, 0}, new int[]{0,-1}, new int[]{-1,0}};
+        int d = 0;
+
+        foreach(char c in instructions){
+            if(c == 'L'){
+                d = (d+3)%4;
+            }else if(c == 'R'){
+                d = (d+1)%4;
+            }else{
+                x += dirs[d][0];
+                y += dirs[d][1];
+            }
+        }
+
+        return x == 0 && y == 0 || d > 0;
+    }
+}