Added LeetCode 46: Permutations (#360)

* Added LeetCode 23: Merge K Sorted Lists

* Added LeetDoe 46: Permutations

* Added LeetCode 46: Permutation

Author: Gaurisha21

CPP/LINKED LIST/SOME LEET CODE QUESTIONS/LeetCode 23.cpp

@@ -0,0 +1,45 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode *merge(ListNode *l1, ListNode *l2)
+    {
+        if(l1==NULL || l2==NULL) return l1==NULL ? l2 : l1; 
+        ListNode *p=new ListNode(-1), *d=p, *c1=l1, *c2=l2;
+        while(c1!=NULL and c2!=NULL)
+        {
+            if(c1->val<=c2->val)
+            {
+                p->next=c1;
+                c1=c1->next;
+            }
+            else
+            {
+                p->next=c2;
+                c2=c2->next;
+            }
+            p=p->next;
+        }
+        p->next = c1!=NULL ? c1 : c2;
+        return d->next;
+    }
+    ListNode *mergeK(vector<ListNode*> lists, int s, int e)
+    {
+        if(s==e) return lists[s];
+        int m=s+((e-s)/2);
+        return merge(mergeK(lists,s,m),mergeK(lists,m+1,e));
+    }
+    ListNode* mergeKLists(vector<ListNode*>& lists) {
+        if(lists.size()==0) return NULL;
+        int n=lists.size();
+        return mergeK(lists,0,n-1);
+    }
+};

CPP/LINKED LIST/SOME LEET CODE QUESTIONS/LeetCode 46.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    int perm(vector<int> nums, vector<vector<int>> &ans, vector<int> &smallAns)
+    {
+        if(smallAns.size()==nums.size())
+        {
+            ans.push_back(smallAns);
+            return 1;
+        }
+        int count=0;
+        for(int i=0; i<nums.size(); i++)
+        {
+            if(nums[i]!=-11)
+            {
+                int temp=nums[i];
+                nums[i]=-11;
+                vector<int> tem = smallAns;
+                tem.push_back(temp);
+                count+=perm(nums,ans,tem);
+                nums[i]=temp;
+            }
+        }
+        return count;
+    }
+    vector<vector<int>> permute(vector<int>& nums) {
+        vector<vector<int>> ans;
+        vector<int> smallAns;
+        int s=perm(nums,ans,smallAns);
+        return ans;
+    }
+};

CPP/recursion/LeetCode 46. Permutations.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    int perm(vector<int> nums, vector<vector<int>> &ans, vector<int> &smallAns)
+    {
+        if(smallAns.size()==nums.size())
+        {
+            ans.push_back(smallAns);
+            return 1;
+        }
+        int count=0;
+        for(int i=0; i<nums.size(); i++)
+        {
+            if(nums[i]!=-11)
+            {
+                int temp=nums[i];
+                nums[i]=-11;
+                vector<int> tem = smallAns;
+                tem.push_back(temp);
+                count+=perm(nums,ans,tem);
+                nums[i]=temp;
+            }
+        }
+        return count;
+    }
+    vector<vector<int>> permute(vector<int>& nums) {
+        vector<vector<int>> ans;
+        vector<int> smallAns;
+        int s=perm(nums,ans,smallAns);
+        return ans;
+    }
+};