DivideTwoIntegers.java

import java.math.BigDecimal;
import java.util.ArrayList;

/** Divide two integers without using multiplication, division and mod operator. */
public class DivideTwoIntegers {
  public int divide(int dividend, int divisor) {
    if (dividend == 0) return 0;
    ArrayList<Integer> list = new ArrayList<Integer>();
    BigDecimal d0 = new BigDecimal(dividend);
    d0 = d0.abs();
    BigDecimal d1;
    BigDecimal d3 = new BigDecimal(divisor);
    d3 = d3.abs();
    int count = 0;
    boolean start = true;
    while (d0.compareTo(d3) == 1 || d0.compareTo(d3) == 0) {
      d1 = new BigDecimal(divisor);
      d1 = d1.abs();
      start = true;
      while (d0.compareTo(d1) == 1 || d0.compareTo(d1) == 0) {
        if (start) {
          list.add(1);
          start = false;
        } else {
          int last = list.get(list.size() - 1);
          list.add(last + last);
        }
        d0 = d0.subtract(d1);
        d1 = d1.add(d1);
      }
    }

    for (int e : list) {
      count += e;
    }

    return (dividend < 0 && divisor < 0) || (dividend > 0 && divisor > 0) ? count : -count;
  }
}