Assignment shivagaur 2215001353

1472DesignBrowserHistory.java

@@ -0,0 +1,34 @@
+class BrowserHistory {
+    List<String> arr=new ArrayList<>();
+    int i=0;
+        public BrowserHistory(String homepage) {
+         arr.add(homepage);  
+         i=0; 
+        }
+        public void visit(String url) {
+         while(arr.size()>i+1){
+            arr.remove(arr.size()-1);
+         }
+         arr.add(url); 
+         i++;
+        }
+        public String back(int steps) {
+            i=Math.max(i-steps,0);
+            return arr.get(i);
+        }
+        public String forward(int steps) {
+            i=i+steps;
+            if(i>=arr.size()){
+                i=arr.size()-1;
+            }
+            return arr.get(i);
+        }
+    }
+
+    /**
+     * Your BrowserHistory object will be instantiated and called as such:
+     * BrowserHistory obj = new BrowserHistory(homepage);
+     * obj.visit(url);
+     * String param_2 = obj.back(steps);
+     * String param_3 = obj.forward(steps);
+     */

2696MinimumStringLengthAfterRemovingSubstrings.java

@@ -0,0 +1,14 @@
+class Solution {
+    public int minLength(String s) {
+        Stack<Character> st=new Stack<>();
+        for(char c:s.toCharArray()){
+            if(!st.isEmpty()){
+                if(st.peek()=='A' && c=='B') st.pop();
+                else if(st.peek()=='C' && c=='D') st.pop();
+                else st.push(c);
+            }
+            else st.push(c);
+        }
+        return st.size();
+    }
+}

682BaseballGame.java

@@ -0,0 +1,22 @@
+class Solution {
+    public int calPoints(String[] operations) {
+        Stack<Integer> stack=new Stack<>();
+        for(String st:operations){
+            if(st.equals("C")) stack.pop();
+            else if(st.equals("D")) stack.push(stack.peek()*2);
+            else if(st.equals("+")){
+                int a=stack.pop();
+                int b=stack.pop();
+                stack.push(b);
+                stack.push(a);
+                stack.push(a+b);
+            }
+            else stack.push(Integer.parseInt(st));
+        }
+        int ans=0;
+        while(!stack.isEmpty()){
+            ans+=stack.pop();
+        }
+        return ans;
+    }
+}

CoinChange.java

@@ -0,0 +1,17 @@
+import java.util.Arrays;
+
+public class CoinChange {
+        public int coinChange(int[] coins, int amount) {
+        int[] dp=new int[amount+1];
+        Arrays.fill(dp,amount+1);
+        dp[0]=0;
+        for(int i=1;i<=amount;i++){
+            for(int j=0;j<coins.length;j++){
+                if(coins[j]<=i){
+                    dp[i]=Math.min(dp[i],dp[i-coins[j]]+1);
+                }
+            }
+        }
+        return dp[amount]>amount?-1:dp[amount];
+    }
+}

CounttheNumberofFairPairs.java

@@ -0,0 +1,49 @@
+import java.util.Arrays;
+
+public class CounttheNumberofFairPairs {
+    public int left(int nums[], int tar){
+        int i =0;
+        int j = nums.length-1;
+        int res = -1;
+        while(i<=j){
+            int mid = (i+j)/2;
+            if(nums[mid]>=tar){
+                res = mid;
+                j = mid-1;
+            }else i = mid+1;
+        }
+        return res;
+    }
+    public int right(int nums[], int tar){
+        int i =0;
+        int j = nums.length-1;
+        int res = -1;
+        while(i<=j){
+            int mid = (i+j)/2;
+            if(nums[mid]<=tar){
+                res = mid;
+                i = mid+1;
+            }else j = mid-1;
+        }
+        return res;
+    }
+    public int solve(int nums[], int l, int r, int i){
+        int left = left(nums,l-nums[i]);
+        if(left==-1) return 0;
+        int right = right(nums,r-nums[i]);
+        if(right==-1) return 0;
+        int diff = (right-left+1);
+        if(left<=i && right>=i) diff--;
+        return diff;
+
+    }
+    public long countFairPairs(int[] nums, int lower, int upper) {
+        Arrays.sort(nums);
+        long res= 0;
+        for(int i=0; i<nums.length; i++){
+            int temp =solve(nums,lower,upper,i);
+            res+=temp;
+        }
+        return res/2;
+    }
+}

Factorial.java

@@ -0,0 +1,15 @@
+
+import java.util.*;
+public class Factorial {
+    public static void main(String[] args) {
+        Scanner sc=new Scanner(System.in);
+        int n=sc.nextInt();
+        System.out.println(fact(n));
+    }
+    public static int fact(int n){
+        if(n==1 || n==0){
+            return 1;
+        }
+        return n*fact(n-1);
+    }
+}

NaturalSum.java

@@ -0,0 +1,17 @@
+
+import java.util.*;
+public class NaturalSum {
+    public static void main(String[] args) {
+        Scanner sc=new Scanner(System.in);
+        int n=sc.nextInt();
+        func(n,1);
+    }
+    public static void func(int n,int n2){
+        if(n==n2){
+            System.out.print(n2);
+            return;
+        }
+        System.out.print(n2+"+");
+        func(n, n2+1);
+    }
+}

Nthfibonacii.java

@@ -0,0 +1,12 @@
+import java.util.*;
+public class Nthfibonacii {
+    public static void main(String[] args) {
+        Scanner sc=new Scanner(System.in);
+        int n=sc.nextInt();
+        System.out.println(func(n));
+    }
+    public static int func(int n){
+        if(n==0 || n==1) return 1;
+        return func(n-1)+func(n-2);
+    }
+}

PowerOf2.java

@@ -0,0 +1,20 @@
+
+
+public class PowerOf2 {
+    public static void main(String[] args) {
+        PowerOf2 p = new PowerOf2();
+        int num = 16;
+        if (p.isPowerOfTwo(num)) {
+            System.out.println(num + " is a power of 2.");
+        } else {
+            System.out.println(num + " is not a power of 2.");
+        }
+    }
+
+    public boolean isPowerOfTwo(int n) {
+        if (n <= 0) {
+            return false;
+        }
+        return (n & (n - 1)) == 0;
+    }
+}