[PDKhan] Week 1

number-of-1-bits/PDKhan.cpp

@@ -0,0 +1,15 @@
+class Solution {
+    public:
+        int hammingWeight(int n) {
+            int cnt = 0;
+
+            while(n){
+                if(n & 1 == 1)
+                    cnt++;
+
+                n >>= 1;
+            }
+
+            return cnt;
+        }
+    };

number-of-islands/PDKhan.cpp

@@ -0,0 +1,29 @@
+class Solution {
+    public:
+        void search(int r, int c, vector<vector<char>>& grid){
+            if(r < 0 || c < 0 || r >= grid.size() || c >= grid[r].size() || grid[r][c] == '0')
+                return;
+
+            grid[r][c] = '0';
+
+            search(r-1, c, grid);
+            search(r+1, c, grid);
+            search(r, c-1, grid);
+            search(r, c+1, grid);
+        }
+
+        int numIslands(vector<vector<char>>& grid) {
+            int cnt = 0;
+
+            for(int i = 0; i < grid.size(); i++){
+                for(int j = 0; j < grid[i].size(); j++){
+                    if(grid[i][j] == '1'){
+                        search(i, j, grid);
+                        cnt++;
+                    }
+                }
+            }
+
+            return cnt;
+        }
+    };

reverse-linked-list/PDKhan.cpp

@@ -0,0 +1,17 @@
+class Solution {
+    public:
+        ListNode* reverseList(ListNode* head) {
+            ListNode* new_head = NULL;
+            ListNode* curr = head;
+
+            while(curr){
+                ListNode* next = curr->next;
+
+                curr->next = new_head;
+                new_head = curr;
+                curr = next;
+            }
+
+            return new_head;
+        }
+    };

two-sum/PDKhan.cpp

@@ -0,0 +1,18 @@
+class Solution {
+    public:
+        vector<int> twoSum(vector<int>& nums, int target) {
+            unordered_map<int, int> Map;
+
+            for(int i = 0; i < nums.size(); i++){
+                int diff = target - nums[i];
+
+                if(Map.find(diff) != Map.end()){
+                    return { Map[diff], i };
+                }
+
+                Map[nums[i]] = i;
+            }
+
+            return {};
+        }
+    };

valid-anagram/PDKhan.cpp

@@ -0,0 +1,20 @@
+class Solution {
+    public:
+        bool isAnagram(string s, string t) {
+            unordered_map<char, int> map;
+
+            if(s.length() != t.length())
+                return false;
+
+            for(int i = 0; i < s.length(); i++)
+                map[s[i]]++;
+
+            for(int i = 0; i < t.length(); i++){
+                if(map[t[i]] == 0)
+                    return false;
+
+                map[t[i]]--;
+            }
+
+            return true;
+        }