Yahoo-Glassdoor

1. Make any given string a palindrome by adding the minimum number of characters.
    http://isharemylearning.blogspot.com/2012/08/minimum-number-of-insertions-in-string.html
    http://blog.csdn.net/atfield/article/details/1496132
    http://blog.csdn.net/atfield/article/details/1496132

2. power of a number (hint: recursion)

3. Describe the file system in hadoop in big view

4. If you are writing a class in Java, "Student" for example; you are storing it in a hashtable; and you want the objects are identical to the names. what can you do?
    http://javarevisited.blogspot.com/2011/02/how-to-write-equals-method-in-java.html

5. Yahoo : 找出最长0,1对数相同的子串
    http://www.1point3acres.com/bbs/thread-12564-1-1.html

6. Yahoo : Find number of black regions in a plane
    http://www.1point3acres.com/bbs/thread-14080-1-1.html

Yahoo-Glassdoor-1.java

/*
adfbd
dbfda

=> d f d

*/
public static String makePalindromeAddLeastChar(String input){
    char[] leftRight = input.toCharArray();
    char[] rightLeft = new char[leftRight.length];
    for(int i = 0; i < leftRight.length; i++) rightLeft[i] = leftRight[leftRight.length - 1 - i];
    int[][] dpMatrix = new int[leftRight.length + 1][leftRight.length + 1];
    for(int i = 0; i < dpMatrix.length; i++){
        for(int j = 0; j < dpMatrix[0].lenght; j++){
            dpMatrix[i][j] = -1;
        }
    }
    int commonLength = LCS(dpMatrix.length - 1, dpMatrix[0].length - 1, leftRight, rightLeft, dpMatrix);
    
    int backTrackRow = dpMatrix.length - 1;
    int backTrackColumn = dpMatrix[0].length - 1;
    
}

public static int LCS(int row, int column, char[] first, char[] second, int[][] dpMatrix[][]){
    if(row == 0 || column == 0) return dpMatrix[row][column] = 0;
    if(dpMatrix[row][column] == -1){
        if(first[row - 1] == second[row - 1]) dpMatrix[row][column] = LCS(row - 1, column - 1, leftRight, rightLeft, dpMatrix) + 1;
        else dpMatrix[row][column] = 
            Math.max(LCS(row - 1, column, leftRight, rightLeft, dpMatrix), LCS(row, column - 1, leftRight, rightLeft, dpMatrix));
    }
    return dpMatrix[row][column];
}

Yahoo-Glassdoor-2.java

//2. power of a number (hint: recursion)

public static double power(int input){
    if(input > 0 ) return (double) powerRecursive(input);
    else return 1d / powerRecursive(input * -1);
}

public static int powerRecursive(int input){
    if(input == 0) return 1;
    int half = input / 2;
    int halfPower = powerRecursive(half);
    if(input % 2 == 1) return ( halfPower * halfPower * 2);
    else return halfPower * halfPower;
}

Yahoo-Glassdoor-4.java

/*
4. If you are writing a class in Java, "Student" for example; you are storing it in a hashtable; and you want the objects are identical to 
the names. what can you do?
*/

public class Student{
    private String name;
    public String getName(){
        return this.name;
    }
    
    @override
    public int hashCode(){
        final int prime = 37;
        int result = 1;
        result = result * prime + (this.name == null? 0 : this.name.hashCode());
        return result;
    }
    
    @override
    public boolean equals(Object obj){
        if(obj == this) return true;
        if(obj == null || obj.getClass() != this.getClass()) return false;
        Student thatStudent = (Student) obj;
        return (this.name == thatStudent.getName() || (this.name != null && this.name.equals(thatStudent.getName())));
    }
}