adding anothe set problem

leetcode/p414_third_max_number.cpp

@@ -0,0 +1,29 @@
+class Solution {
+public:
+    int thirdMax(vector<int>& nums) {
+        std::set<int> set1;
+        int size = nums.size();
+        // create the set, the difference between set1 and nums is that elements in set1 is unique and is sorted.
+        for(int i=0;i<size;i++){
+            set1.insert(nums[i]);
+        }
+
+        std::set<int>::iterator itr1 = set1.end();
+        int result;
+        itr1--;
+        result = *itr1; // store the max number
+        // if 3rd max doesn't exist
+        if(itr1==set1.begin()){
+            return result;
+        }
+        itr1--;
+        // still, if 3rd max doesn't exist
+        if(itr1==set1.begin()){
+            return result;
+        }
+        itr1--;
+        // get the 3rd max
+        result = *itr1;
+        return result;
+    }
+};