Create 136_single_number.cpp

Author: Rashed112

solutions/136_single_number.cpp

@@ -0,0 +1,45 @@
+//Solution-1: 
+//Time: O(nlogn), Space: O(1)
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        if(nums.size()==1){
+            return nums[0];
+        }
+        int i=0,res = 0;
+        while(i<nums.size()-1){
+            if(nums[i] == nums[i+1]){
+                i+=2;
+            }
+            else{
+                res = i;
+                break;
+            }
+            if(i==nums.size()-1){
+                res = i;
+            }
+        }
+        return nums[res];    
+    }
+};
+
+//Solution-2: Using Bitwise XOR operation 
+//Time: O(n), Space: O(1)
+class Solution {
+public:
+    /*
+    XOR's properties,
+    1. a^a=0
+    2. a^b^a=b
+    3. (a^a^b) = (b^a^a) = (a^b^a) = b 
+    4. Similarly, a^a^a.... (even times)=0 and a^a^a....(odd times)=a
+    */
+    int singleNumber(vector<int>& nums) {
+        int res = 0;
+        for(auto x: nums){
+            res^=x;
+        } 
+        return res;
+    }
+};