Interview Question Sparse Vector

SparseVector

//Given two sparse vectors. Write a function to find a dot product of these vectors.

// [0,4,0,0,1,0,0,10,0] 
// [2,0,0,0,3,0,0,0,0]

// 3

x = (4, 1), (1, 4), (10, 7)
y = (2, 0), (3, 4)

public int dot(double[] x, double[] y) throws Exception {
    if(x.length != y.length) {
        throw new Exception("Error in dot product: x and y are not of equal length");
    }

    double dotproduct = 0;
    for(int i = 0; i < x.length; i++) {
        dotproduct += x[i] * y[i];
    }
    return dotproduct;
}

class SparseVectorEntry {

    private int position;
    private int value;

    public SparseVectorEntry(int value, int position) {
        this.position = position;
        this.value = value;
    }

    public int getPosition() {
        return position;
    }
    
    public int getValue() {
        return value;
    }
    
    public void setPosition(int position) {
        this.position = position;
    }
    
    public void setValue(int value) {
        this.value = value;
    }
}

x = (4, 1), (1, 4), (10, 7)
y = (2, 0), (3, 4)

public int dot(SparseVectorEntry[] x, SparseVectorEntry[] y) {
    int pointerX = 0;
    int pointerY = 0;
    double dotproduct = 0;
    while(pointerX < x.length && pointerY < y.length) {
        if(x[pointerX].getPosition() < y[pointerY].getPosition()) {
            pointerX++;
        } else if(x[pointerX].getPosition() > y[pointerY].getPosition()) {
            pointerY++;
        } else {
            dotproduct += x[pointerX].getValue() * y[pointerY].getValue();
            positionX++;
            positionY++;
        }
    }
    return dotproduct;
    
}