Converting an integer to binary string - Binary.java

/*************************************************************************
 *  Compilation:  javac Binary.java
 *  Execution:    java Binary n
 *  
 *  Prints out n in binary.
 * 
 *  % java Binary 5
 *  101
 *
 *  % java Binary 106
 *  1101010
 *
 *  % java Binary 0
 *  0
 * 
 *  % java Binary 16
 *  10000
 *
 *  Limitations
 *  -----------
 *  Does not handle negative integers.
 *
 *  Remarks
 *  -------
 *  could use Integer.toBinaryString(N) instead.
 *
 *************************************************************************/

public class Binary { 
    public static void main(String[] args) { 

        // read in the command-line argument
        int n = Integer.parseInt(args[0]);

        // set v to the largest power of two that is <= n
        int v = 1;
        while (v <= n/2) {
            v = v * 2;
        }
  
        // check for presence of powers of 2 in n, from largest to smallest
        while (v > 0) {

            // v is not present in n 
            if (n < v) {
                System.out.print(0);
            }

            // v is present in n, so remove v from n
            else {
                System.out.print(1);
                n = n - v;
            }

            // next smallest power of 2
            v = v / 2;
        }

        System.out.println();

    }

}

Though written a program, we can use inbuilt lib of java - See here.

Input functions in java (UDFs)

Inputing strings
public int inputInt() throws IOException
{
    int k=0;
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String str;
    str = br.readLine();
    k = Integer.parseInt(str);
    return k;
           
}
For inputing integers
public int inputInt() throws IOException
{
    int k=0;
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String str;
    str = br.readLine();
    k = Integer.parseInt(str);
    return k;
           
}

LCS in java

/**  Reads in two strings from stdin and computes their longest
 *  common subsequence.

see inputString function here. 

------------------------------------------------------------------*/  

public class LCS {

    public static void main(String[] args) {
        String x = inputString();
        String y = inputString();
        int M = x.length();
        int N = y.length();

        // opt[i][j] = length of LCS of x[i..M] and y[j..N]
        int[][] opt = new int[M+1][N+1];

        // compute length of LCS and all subproblems via dynamic programming
        for (int i = M-1; i >= 0; i--) {
            for (int j = N-1; j >= 0; j--) {
                if (x.charAt(i) == y.charAt(j))
                    opt[i][j] = opt[i+1][j+1] + 1;
                else 
                    opt[i][j] = Math.max(opt[i+1][j], opt[i][j+1]);
            }
        }

        // recover LCS itself and print it to standard output
        int i = 0, j = 0;
        while(i < M && j < N) {
            if (x.charAt(i) == y.charAt(j)) {
                System.out.print(x.charAt(i));
                i++;
                j++;
            }
            else if (opt[i+1][j] >= opt[i][j+1]) i++;
            else                                 j++;
        }
        System.out.println();

    }

}