diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..58461f25
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.ipynb_checkpoints
\ No newline at end of file
diff --git a/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 1.ipynb b/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 1.ipynb
index af95adee..ef4284e3 100644
--- a/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 1.ipynb	
+++ b/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 1.ipynb	
@@ -688,7 +688,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -702,7 +702,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.5"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,
diff --git a/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 2.ipynb b/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 2.ipynb
index 2869d82b..13e8f8ad 100644
--- a/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 2.ipynb	
+++ b/Module 1 - Python Programming/12. Problem Solving for Interviews/Problem Solving Part 2.ipynb	
@@ -21,13 +21,74 @@
     "```"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Hint: Sort an array and take difference of max and min element <br>\n",
+    "Time Complexity *O(nlogn)* for sorting the array"
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 26,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "11"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "def solve(arr):\n",
+    "    arr.sort(reverse=True)\n",
+    "    ans = arr[0]-arr[-1]\n",
+    "    return ans\n",
+    "arr = [0, -1, 5, 7, 10]\n",
+    "solve(arr)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Can it be further optimised? Think!<br>\n",
+    "Can we do it with *O(n)* complexity"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 27,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "11"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
-    "## Solution"
+    "arr = [0, -1, 5, 7, 10]\n",
+    "def solve(arr):\n",
+    "    max_so_far, min_so_far = -10000007,10000007\n",
+    "    for num in arr:\n",
+    "        if num>max_so_far:\n",
+    "            max_so_far=num\n",
+    "        if num<min_so_far:\n",
+    "            min_so_far=num\n",
+    "    return (max_so_far-min_so_far)\n",
+    "solve(arr)"
    ]
   },
   {
@@ -49,11 +110,32 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 28,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "3"
+      ]
+     },
+     "execution_count": 28,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
-    "## Solution"
+    "## Solution\n",
+    "\n",
+    "arr = [3,1,2,5,3]\n",
+    "def solve(arr):\n",
+    "    hashmap = {}\n",
+    "    for num in arr:\n",
+    "        if hashmap.get(num,0)==1:\n",
+    "            return num\n",
+    "            break\n",
+    "        hashmap[num]=1\n",
+    "solve(arr) "
    ]
   },
   {
@@ -72,17 +154,61 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 33,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "6"
+      ]
+     },
+     "execution_count": 33,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
-    "## Solution"
+    "## Solution\n",
+    "# Approach to track right max and left max at each position and remove height of bar from each to get total water at each location\n",
+    "height = [0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1]\n",
+    "\n",
+    "def solve(height):\n",
+    "    n = len(height)\n",
+    "    right_max = [0]*n\n",
+    "    left_max = [0]*n\n",
+    "    \n",
+    "    # calulate left max at each location\n",
+    "    left_max[0] = height[0]\n",
+    "    for i in range(1,n):\n",
+    "        left_max[i]=max(left_max[i-1], height[i])\n",
+    "        \n",
+    "    # calulate right max at each location\n",
+    "    right_max[n-1]= height[n-1]\n",
+    "    for i in range(n-2,0,-1):\n",
+    "        right_max[i]=max(right_max[i+1], height[i])\n",
+    "\n",
+    "    # total water trapped min(left_max,right_max)-height of bar at location\n",
+    "    water = 0\n",
+    "    for i in range(n):\n",
+    "        water+=min(right_max[i],left_max[i])-height[i]\n",
+    "    \n",
+    "    return water\n",
+    "\n",
+    "solve(height)"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -96,7 +222,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.5"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,