HW1_done #14

OlgaBerezhna · 2016-11-27T18:47:28Z

HW_1 corrected

xSAVIKx · 2016-11-27T19:09:30Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task6.java

@@ -2,10 +2,13 @@

 public class Task6 {
    public static double calculateS(double x) {
-        return 0d;
-    }
+        return (1 + (x * (((Math.pow(x, 2) *x) *x) / (2 * (3*2) * (4*3*2)))));


It's not correct solution.
Try to solve it step-by-step.
Also you can take look at other students solutions.

xSAVIKx · 2016-11-27T19:12:10Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task10.java

+            if (n / 10 == 10) {
+                return true;
+            }
+        }


It's not correct solution.
It'll loop forever for some numbers, for example, when n=27:

n>0 -> true -> go into while loop

n%10 == 2 -> false -> do not divide n by 10 -> go to step 1.

xSAVIKx · 2016-11-27T19:13:29Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task3.java

-        return false;
+
+        if ((a <= b && b <= c) || (a >= b && b >= c)) return true;
+        else return false;


You don't need if-else statement here as the result of your expression is boolean - so just return your expression.

xSAVIKx · 2016-11-27T19:14:27Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task4.java

+                 }
+
+
+        }


Please format you code before commit, you can use IDEA shortcut: CTRL+ALT+L.

xSAVIKx · 2016-11-27T19:16:02Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task5.java

@@ -3,10 +3,10 @@

 public class Task5 {
    public static double calculateA(double x, double y, double z) {
-        return 0;
+        return ((2 * Math.sin(x - Math.PI / 6) * calculateB(z)) / (1 / 2.0 + (Math.pow(Math.sin(y), 2))));


It's quite hard to read such expressions. It'll be easier for understanding if you'll split it into some pretty parts, like top-part of expression, bottom-part of expression.

But, anyway, it do pass all the tests.

xSAVIKx · 2016-11-27T19:17:18Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task7.java

+                dayNumber = "Error";
+                break;
+        }
+        return dayNumber;


There's no need for dayNumber variable here. Just do return in each case clause.
Also, you should return Error in lowercase to pass the test.

xSAVIKx · 2016-11-27T19:20:54Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task9.java

+        while (n % 3 == 0) {
+            boolean b = (n / 3) == 3;
+        }
+            return true;


This implementation doesn't work.
You need to re-assign value of n/3 back to n, cause right now you'll have infinite loop in many cases.

xSAVIKx · 2016-11-28T11:57:02Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task6.java

@@ -2,10 +2,16 @@

 public class Task6 {
    public static double calculateS(double x) {
-        return (1 + (x * (((Math.pow(x, 2) *x) *x) / (2 * (3*2) * (4*3*2)))));
+        return (1 + (x * (((Math.pow(x, 2) *x) *x) / (factorial(2)*factorial(3)*factorial(4)))));


Your task is to calculate: 1 + x + x^2/2! + x^3/3! + x^4/4!
And you are trying to calculate: 1 + (x * x^2 * x * x) / (2! * 3! * 4!)

xSAVIKx · 2016-11-28T12:32:01Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task6.java

+        for (int i = 1; i <= n; i++) {
+            n = n * i;
+            }
+            return n;


Your factorial function doesn't return correct result.
Try to calculate on your own with n=2:

i=1; n=2; i>=n -> true; n=n*i; i++

i=2; n=2; i>=n -> true; n=n*i; i++

i=3; n=4; i>=n -> true; n=.....

As you see - you'll loop until you'll get overflow on int value and number will be negative.

xSAVIKx · 2016-11-28T14:27:43Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task7.java

+                return "Sunday";
+
+            default:
+                return  "Error";


you should return error in lowercase: "error"

xSAVIKx · 2016-11-28T14:29:06Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task8.java

+        int result = 0;
+        int i;
+        for (i = N; 2 * N >= i; i++)
+            result = (int) (i + Math.pow((2 * N), 2));


Check task description again.
You should calculate: N^2 + (N+1)^2 + (N+2)^2+ ... + (N+N)^2

xSAVIKx · 2016-11-28T14:29:50Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task9.java

+        while (n % 3 == 0) {
+            n = n / 3;
+        }
+            return true;


Check again that your solution do pass all the given test cases.
For example, if n=15 you'll return true, while 15 is not power of 3.

xSAVIKx

Please fix error with 3^0.

xSAVIKx · 2016-12-01T19:00:46Z

src/main/java/school/lemon/changerequest/java/introduction/hw1/Task9.java

@@ -4,14 +4,14 @@

    public static boolean isPowerOfThree(int n) {

-        if (n < 1){
+        if (n <= 1){


1 is 3^0 - and due to given condition you'll return false

OlgaBerezhna added 12 commits November 27, 2016 15:50

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OlgaBerezhna added 6 commits November 27, 2016 22:01

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OlgaBerezhna added 3 commits December 1, 2016 18:31

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HW1_done #14

HW1_done #14

OlgaBerezhna commented Nov 27, 2016 •

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HW1_done #14

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HW1_done #14

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OlgaBerezhna commented Nov 27, 2016 • edited Loading

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OlgaBerezhna commented Nov 27, 2016 •

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