Problem Solving

Java-DSA.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$" isTestSource="false" packagePrefix="Java_DSA" />
+      <sourceFolder url="file://$MODULE_DIR$/Collection Framework" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/Recursion" isTestSource="false" packagePrefix="Java_DSA.Searching" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

Problems/Arrays/FirstAndLastPositionOfElement.java

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+package Java_DSA.Problems.Arrays;
+
+import java.util.* ;
+import java.io.*;
+public class FirstAndLastPositionOfElement {
+
+    public static int[] firstAndLastPosition(ArrayList<Integer> arr, int n, int k) {
+        // Write your code here.
+        ArrayList<Integer>list = new ArrayList<>();
+        for(int i = 0;i < n;i++){
+            if(arr.get(i) == k){
+                list.add(i);
+            }
+        }
+        int[] ans = new int[2];
+        if(list.size()==0){
+         ans[0] = -1;
+         ans[1] = -1;
+         return ans;
+        }
+        ans[0] = Collections.min(list);//list.get(0);
+        ans[1] = Collections.max(list);//list.get(list.size()-1);
+        return ans;
+    }
+
+    public static void main(String[] args) {
+        ArrayList<Integer>l = new ArrayList<>(List.of(0,0,1,1,2,3,2,2,2));
+        int[] result = firstAndLastPosition(l,l.size(),2);
+        for (int j : result) {
+            System.out.print(j + " ");
+        }
+    }
+
+};

Problems/Arrays/IntersectionOfArrays.java

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+package Java_DSA.Problems.Arrays;
+
+import java.util.* ;
+import java.io.*;
+public class IntersectionOfArrays
+{
+    public static ArrayList<Integer> findArrayIntersection(ArrayList<Integer> arr1, int n, ArrayList<Integer> arr2, int m)
+    {
+
+        // Write Your Code Here.
+        ArrayList<Integer>list = new ArrayList<>();
+        //initializing pointers to 0
+        int i = 0;
+        int j = 0;
+        while(i < n && j < m){
+            if(arr1.get(i).equals(arr2.get(j)))//use equals to check same value bcz if u use == it checks object.
+            {
+                list.add(arr1.get(i));
+                i++;
+                j++;
+            }
+            else if(arr1.get(i) < arr2.get(j))//since array is sorted so increment first array pointer if value is less than value in 2nd array
+            {
+                i++;
+            }
+            else{
+                j++;
+            }
+        }
+        if(list.size()== 0)
+            list.add(-1);
+
+        return list;
+    }
+
+    public static void main(String[] args) {
+
+        ArrayList<Integer> ans = new ArrayList<>();
+
+        ArrayList<Integer>l1 = new ArrayList<>(List.of(1,2,2,2,3,4));
+        ArrayList<Integer>l2 = new ArrayList<>(List.of(2,2,3,3));
+//        ArrayList<Integer>l1 = new ArrayList<>(List.of(3,4));
+//        ArrayList<Integer>l2 = new ArrayList<>(List.of(2,2));
+        ans = findArrayIntersection(l1,l1.size(),l2,l2.size());
+
+        System.out.println(ans);
+    }
+}

Problems/Arrays/RotateArray.java

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+//Sample Input 1:
+//        8
+//        7 5 2 11 2 43 1 1
+//        2
+//Sample Output 1:
+//        2 11 2 43 1 1 7 5
+//Explanation Of Sample Input 1:
+//Rotate 1 steps to the left: 5 2 11 2 43 1 1 7
+//Rotate 2 steps to the left: 2 11 2 43 1 1 7 5
+//
+
+package Java_DSA.Problems.Arrays;
+
+import java.util.* ;
+import java.io.*;
+class RotateArray {
+    public static void main(String args[]) {
+        Scanner in=new Scanner(System.in);
+        int n=in.nextInt();
+        int arr[]=new int[n];
+        for(int i=0 ; i<n ; i++){
+            arr[i]=in.nextInt();
+        }
+        int r=in.nextInt();
+        for(int i=0 ; i<r ; i++){
+            int temp=arr[0];
+            for(int j=1 ; j<n ; j++){
+                arr[j-1]=arr[j];
+            }
+            arr[n-1]=temp;
+        }
+        for(int i=0 ; i<n ; i++){
+            System.out.print(arr[i]+" ");
+        }
+    }
+}
+

Problems/Arrays/Sort012.java

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+//Given an array which only contains 0,1 and 2 and we have to sort it.
+//Sample Input 1 :
+//        2
+//        6
+//        0 1 2 2 1 0
+//        7
+//        0 1 2 1 2 1 2
+// Sample Output 1 :
+//        0 0 1 1 2 2
+//        0 1 1 1 2 2 2
+// Sample Input 2 :
+//        2
+//        7
+//        2 2 2 1 1 1 0
+//        6
+//        2 1 2 0 1 0
+// Sample Output 2 :
+//        0 1 1 1 2 2 2
+//        0 0 1 1 2 2
+
+package Java_DSA.Problems.Arrays;
+import java.util.* ;
+import java.io.*;
+public class Sort012
+{
+    public static void sort012(int[] arr)
+    {
+        int count0=0;
+        int count1=0;
+        int count2=0;
+
+        for(int num:arr){
+            if(num==0)
+                count0++;
+            else if(num==1)
+                count1++;
+            else
+                count2++;
+        }
+        for(int i=0;i<arr.length;i++){
+            if(i<count0)
+                arr[i]=0;
+            else if(i<count0+count1)
+                arr[i]=1;
+            else
+                arr[i]=2;
+        }
+    }
+}

Problems/Arrays/TwoSum.java

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+//Sample Input 1 :
+//        2
+//        4 9
+//        2 7 11 13
+//        5 1
+//        1 -1 -1 2 2
+//Sample Output 1:
+//        2 7
+//        -1 2
+//        -1 2
+//Explanation For Sample 1:
+//For the first test case, we can see that the sum of  2 and 7 is equal to 9 and it is the only valid pair.
+//For the second test case, there are two valid pairs (-1,2) and (-1,2), which add up to 1.
+//
+//Sample Input 2 :
+//        1
+//        4 16
+//        2 7 11 13
+//Sample Output 2 :
+//        -1 -1
+//
+//package Java_DSA.Problems.Arrays;
+//import java.util.ArrayList;
+//import java.util.HashMap;
+//import java.util.*;
+//
+
+
+
+//public class TwoSum {
+//    static ArrayList<Pair<Integer, Integer>> twoSum(ArrayList<Integer> arr, int target, int n) {
+//        // Write your code here.
+//
+//        ArrayList<Pair<Integer,Integer>>list = new ArrayList<>();
+//        int i = 0;
+//        int j = n-1;
+//        Collections.sort(arr);
+//
+//        while(i < j){
+//            if((arr.get(i)+arr.get(j))== target){
+//                list.add(new Pair(arr.get(i),arr.get(j)));
+//                i++;
+//                j--;
+//            }
+//            else if((arr.get(i)+arr.get(j)) <  target){
+//                i++;
+//            }
+//            else{
+//                j--;
+//            }
+//        }
+//        if(list.isEmpty())
+//            list.add(new Pair(-1,-1));
+//
+//        return list;
+//    }
+//}