1. Reverse of an Arrays

public static void reverse(int arr[]) {
        int low = 0;
        int high = arr.length -1;
        while (low < high) {
            int temp = arr[low];
            arr[low] = arr[high];
            arr[high] = temp;
            low++;
            high--;
        }
    }

1. Remove duplicates from sorted Arrays

public static int removeduplicate(int arr[]) {
        Arrays.sort(arr);
        int ans = 1;
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] != arr[ans-1]) {
                arr[ans] = arr[i];
                ans++;
            }
        }
        return ans;
    }

1. Find Minimum and Maximum element in an array

 public static void minANDmax(int arr[]) {
        if (arr == null || arr.length == 0) {
            return;
        }
        int min = arr[0];
        int max  = arr[0];
        for (int i = 1; i < arr.length; i++) {
            if (arr[i] < min) {
                min = arr[i];
            }
            if (arr[i] > max) {
                max = arr[i];
            }
            // min = Math.min(min, arr[i]);
            // max = Math.max(max, arr[i]);
        }
        System.out.println("Min : " + min);
        System.out.println("Max : " + max);
    }

1. Richest Customer Wealth

public static int wealth(int arr[][]) {
        int ans = Integer.MIN_VALUE; // -Infinity
        for (int row = 0; row < arr.length; row++) {
            //when start a col , take sum of row
            int sum = 0;
            for (int col = 0; col < arr[row].length; col++) {
                sum = sum + arr[row][col];
            }
            if (sum > ans) {
                ans = sum;
            }
        }
        return ans;
    }

1. Find Smallest Letter in the Array Greater than Target

1. Move all Zeros to End

 public static int[] movezero(int arr[]) {
        int count = 0;
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] != 0) {
                int temp = arr[i];
                arr[i] = arr[count];
                arr[count] = temp;
                count++;
            }
        }
        return arr;
    }

1. Left Rotate an array by one

public static int[] leftrotate(int arr[]) {
        int temp = arr[0];
        for (int i = 1; i < arr.length; i++) {
            arr[i-1] = arr[i];
        }
        arr[arr.length-1] = temp;
        return arr;
    }

1. Left Rotate an array by K

{
    // Function to rotate an array by d elements in counter-clockwise direction.
    static void rotateArr(int arr[], int d, int n) {
        // add your code here
              
        int temp[] = new int[n];
        for(int i=0 ; i<n ; i++){
            
            int j = i-d;//to decrease index by d
            
            while(j<0){  //if j is -ve we have make it +ve                                              index by adding with arr size
                j = j+n;
            }
            temp[j] = arr[i];  
        }
        
        for(int i=0; i<n; i++){  
            arr[i] = temp[i];
        }
    }
}

1. leader in an Array

public static void leader(int arr[]) {
        //a leader has to be greater than all the elements in right side
        int curr_l = arr[arr.length - 1];
        System.out.println(curr_l);
        for (int i = arr.length-2; i >= 0; i--) {
            if(curr_l < arr[i]){
                curr_l = arr[i];
                System.out.println(curr_l);
            }
        }
    }