while loop adding an extra when input is 0

Question

I am working in java. I am trying to do the below problem from code wars. I have provided my solution at the bottom.

QUESTION: In a small town the population is p0 = 1000 at the beginning of a year. The population regularly increases by 2 percent per year and moreover 50 new inhabitants per year come to live in the town. How many years does the town need to see its population greater or equal to p = 1200 inhabitants?

At the end of the first year there will be: 1000 + 1000 * 0.02 + 50 => 1070 inhabitants

At the end of the 2nd year there will be: 1070 + 1070 * 0.02 + 50 => 1141 inhabitants (** number of inhabitants is an integer **)

At the end of the 3rd year there will be: 1141 + 1141 * 0.02 + 50 => 1213

It will need 3 entire years. More generally given parameters:

p0, percent, aug (inhabitants coming or leaving each year), p (population to surpass)

the function nb_year should return n number of entire years needed to get a population greater or equal to p.

aug is an integer, percent a positive or null floating number, p0 and p are positive integers (> 0)

Examples: nb_year(1500, 5, 100, 5000) -> 15 nb_year(1500000, 2.5, 10000, 2000000) -> 10 Note: Don't forget to convert the percent parameter as a percentage in the body of your function: if the parameter percent is 2 you have to convert it to 0.02.

MY SOLUTION:

public static int nbYear(int p0, double percent, int aug, int p) {
  System.out.println("p0 : "+p0 +"percent"+percent+"aug"+aug+"p: "+p);
  double tmp = p0*(1+(percent/100))+aug;
  System.out.println("running total: " +tmp);
  int i=1;
  while (tmp<=p){
    tmp =  tmp * (1+(percent/100)) + aug;
    System.out.println("running total: " +tmp);
    i++;
  }
  return i;

}

THE ISSUE:

I am getting the answer 51 with the following inputs. The answer should be 50.
p0= 1500000 ,percent = 0.0, aug = 10000, p =2000000 nbYear(1500000 , 0.0, 1000, 2000000)

Form the statements I am printing to the console, I can see that running total is 2000000 at some point. However, the while loop does not break and I don't understand why. Can you help? See below for console logs.

p0 : 1500000percent0.0aug10000p: 2000000
running total: 1510000.0
running total: 1520000.0
running total: 1530000.0
running total: 1540000.0
running total: 1550000.0
running total: 1560000.0
running total: 1570000.0
running total: 1580000.0
running total: 1590000.0
running total: 1600000.0
running total: 1610000.0
running total: 1620000.0
running total: 1630000.0
running total: 1640000.0
running total: 1650000.0
running total: 1660000.0
running total: 1670000.0
running total: 1680000.0
running total: 1690000.0
running total: 1700000.0
running total: 1710000.0
running total: 1720000.0
running total: 1730000.0
running total: 1740000.0
running total: 1750000.0
running total: 1760000.0
running total: 1770000.0
running total: 1780000.0
running total: 1790000.0
running total: 1800000.0
running total: 1810000.0
running total: 1820000.0
running total: 1830000.0
running total: 1840000.0
running total: 1850000.0
running total: 1860000.0
running total: 1870000.0
running total: 1880000.0
running total: 1890000.0
running total: 1900000.0
running total: 1910000.0
running total: 1920000.0
running total: 1930000.0
running total: 1940000.0
running total: 1950000.0
running total: 1960000.0
running total: 1970000.0
running total: 1980000.0
running total: 1990000.0
running total: 2000000.0
running total: 2010000.0

expected:<50> but was:<51>

Elliott Frisch · Answer

Computer programmers start counting at 0 (not 1). Change int i = 1; to int i = 0;, second I would make the test and assignment of tmp to p in the while loop condition. I would also use formatted output over string concatenation. Like,

public static int nbYear(int p0, double percent, int aug, int p) {
    System.out.printf("p0: %d, percent: %.2f, aug: %d, p: %d%n",
            p0, percent, aug, p);
    double tmp = p0;
    int i = 0;
    while ((tmp = tmp * (1 + (percent / 100)) + aug) <= p) {
        System.out.println("running total: " + tmp);
        i++;
    }
    return i;
}

while loop adding an extra when input is 0

1 Answers