Two-Pointers

Author: Shikha-code36

Two-pointers/twopointer.ipynb

@@ -0,0 +1,182 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "True\n"
+     ]
+    }
+   ],
+   "source": [
+    "#if string is palindrome\n",
+    "\n",
+    "def ispalindrome(s):\n",
+    "    #start\n",
+    "    i=0\n",
+    "    #end\n",
+    "    j=len(s)-1\n",
+    "    while i<j:\n",
+    "        if s[i]!=s[j]:\n",
+    "            return False\n",
+    "        \n",
+    "        i=i+1\n",
+    "        j=j-1\n",
+    "    return True\n",
+    "\n",
+    "print(ispalindrome(\"civic\")) #True"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "True\n"
+     ]
+    }
+   ],
+   "source": [
+    "#sum of element of sorted array is equal to target\n",
+    "\n",
+    "def twosum(arr,target):\n",
+    "    #start \n",
+    "    i=0\n",
+    "    #end\n",
+    "    j=len(arr)-1\n",
+    "    while i<j:\n",
+    "        sum = arr[i]+arr[j]\n",
+    "        if target == sum:\n",
+    "            return True\n",
+    "        elif sum<target:\n",
+    "            i=i+1\n",
+    "        else:\n",
+    "            j=j-1\n",
+    "    return False\n",
+    "\n",
+    "print(twosum([4,6,9,10,12,18,22],19))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "7\n"
+     ]
+    }
+   ],
+   "source": [
+    "#Two Pointer Technique In sorted Array and Binary Search\n",
+    "\n",
+    "def sum(arr,key):\n",
+    "    l=0\n",
+    "    r=len(arr)-1\n",
+    "    while l<=r:\n",
+    "        m=(l+r)//2\n",
+    "        if arr[m]==key:\n",
+    "            return m\n",
+    "        elif arr[m]<key:\n",
+    "            l=m+1\n",
+    "        else:\n",
+    "            #arr[m]>key\n",
+    "            r=m-1\n",
+    "    return -1\n",
+    "\n",
+    "print(sum([6,8,9,10,12,42,51,65,82],65))    "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "7"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "#inbuilt function- bisect acts as a binary search\n",
+    "import bisect\n",
+    "arr = [6,8,9,10,12,42,51,65,82]\n",
+    "key = 65\n",
+    "bisect.bisect_left(arr,key)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[8, 2]\n"
+     ]
+    }
+   ],
+   "source": [
+    "#Two Pointer Technique In unsorted Array\n",
+    "\n",
+    "def findtarget(arr,target):\n",
+    "    st =set() #unordered data structure can take hashmap here \n",
+    "\n",
+    "    for i in range(len(arr)):\n",
+    "        complement = target - arr[i]\n",
+    "        if complement in st:\n",
+    "            return [complement,arr[i]]\n",
+    "        else:\n",
+    "            st.add(arr[i])\n",
+    "print(findtarget([8,2,9,3,6,4,13,41,15],10))"
+   ]
+  }
+ ],
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+   "display_name": "Python 3.9.7 64-bit",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
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+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.7"
+  },
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+  "vscode": {
+   "interpreter": {
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