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I have two arrays a[] and b[].
int a[]={3,1,1,1,7,4,6,6,3,1};
int b[]=new int[a.length];
Array length in actual problem can change.
The values in the array must be less then value of array length as seen.
The output must be:
b = 3 1 0 0 7 4 6 0 3 1
So basically if there is a sequence of same value in a[] then only 1st of its value must be placed at same index in b[] rest should be zero till the sequence exists.
Answer in java syntax will be helpful.
Thank you in advance
int a[]={3,1,1,1,7,4,6,6,3,1};
int b[]=new int[a.length];
int temp = a[0];
b[0] = temp;
for(int i = 1; i < a.length; i++) {
if(a[i] == temp)
b[i] = 0;
else
b[i] = a[i];
temp = a[i];
}
hint:
1) create hashmap to store processed values
2) iterate over the first array: if current value is stored in map, then fill 0, otherwise store this value in HashMap and copy the value to new array
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Short question. I am quite new to doing bit/bytewise operations in Java, but I noticed something strange.
The code below gives as output:
2
0
code:
String[] nodes = new String[3];
boolean in;
int index = 0;
int hash = "hi".hashCode();
in = (nodes[(index = nodes.length - 1) & hash]) != null;
System.out.println(index);
index = (nodes.length - 1) & hash;
System.out.println(index);
Why is it, that index has a different value even though the operation to assign a value to index is identical in the 5th and 7th line of code?
Like I said, I'm new to bitwise/bytewise operations so I'm probably missing some background information.
(index = nodes.length - 1) & hash
assigns nodes.length - 1 to index, then bitwise-ands it with hash.
index = (nodes.length - 1) & hash
bitwise-ands nodes.length - 1 with hash, then assigns the result to index.
Not the same thing.
Your first assigment to index happens in the parenthesis here:
in = (nodes[(index = nodes.length - 1) & hash]) != null;
Which is
index = nodes.length - 1
and has a value of "two". Your second assignment (index = (nodes.length - 1) & hash;) differs; you added a & hash which presumably has the two bit as 0 thus when you perform the bitwise & it becomes 0.
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I wrote the following code to sort the elements in the array values using a BubbleSort. Is this correct or is there anything missing? My test cases are good, but maybe it's the test cases that are also missing something.
public void sort(ValuePair[] values) {
ValuePair value = null;
for (int i = 0; i < values.length; i++) {
for (int j = 1 + i; j < values.length; j++) {
if (values[i].getValue() > values[j].getValue()) {
value = values[j];
values[j] = values[i];
values[i] = value;
}
}
}
}
Your code is correct in that it will sort the array. However it will always require N*(N-1) passes over the array. This is not
the typical algorithm used to implement
a bubble sort. The typical algorithm uses repeat loop with a test for sorted. This is somewhat more efficient because it
terminates as soon as the array is sorted (consider the case where you start with a sorted array).
Read the Wikepedia article on bubble sort it demonstrates this very well.
A somewhat improved version pseudocode version of Bubble Sort goes something like this:
procedure bubbleSort( A : list of sortable items )
n = length(A)
repeat
swapped = false
for i = 1 to n-1 inclusive do
if A[i-1] > A[i] then
swap(A[i-1], A[i])
swapped = true
end if
end for
n = n - 1
until not swapped
end procedure
The lesson here is that while your algorithm and the Wikepedia algorithm both have the same big O characteristics, a small change
in the way they have been implemented can make a significant difference in their actual performance characteristics.
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I'm trying to figure how to find the largest number in an array of random numbers.
So far I cant manage to get it right.
Its an array[50] and the random, numbers are between 0-100.
Thanks!
Loop through the array and keep track of the largest number found already in an int variable.
public int findMax(int[] numbers)
{
int max = 0;
for (int i = 0; i < numbers.length; ++i)
if (numbers[i] > max) max = numbers[i];
return max;
}
(You can also initialize max to int.MIN_VALUE or something if it helps behave more suitably in the case where an empty array is passed in.)
Use:
java.utils.Arrays.sort(yours_array);
int largest = yours_array[yours_array.length - 1] ;
Collections.max and you can use it as follows with a raw array:
List<Integer> triedArray = new ArrayList<Integer>();
ArrayUtils.addAll(intArray);
This does add a dependency on commons-lang, though.
Assuming the int[] is named array
Try to use a loop like the following:
int biggest = array[0]
for(int a = 1; a < array.length; a++){
if(array[a] > biggest){
biggest = array[a]
}
}
At the end, your variable biggest will hold the largest value in the array.
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Why it doesn't work?
P.S. I am beginner in Java.
int userInfo[];
userInfo = new int[2];
userInfo[0] = 11;
userInfo[1] = 20;
userInfo["result"] = userInfo[0] + userInfo[1];
System.out.println(userInfo["result"]);
Only an int can be an index into an array. A String won't work. If you need 3 slots, declare your array to be length 3 and then you can use userInfo[2].
The JLS, Section 10.4 makes it pretty clear:
Arrays must be indexed by int values; short, byte, or char values may also be used as index values because they are subjected to unary numeric promotion (§5.6.1) and become int values.
int userInfo[];
userInfo = new int[2];
userInfo[0] = 11;
userInfo[1] = 20;
int result = userInfo[0] + userInfo[1];
System.out.println(result);
The string can not be the index in array.
Your array has 2 slots, and you used them to store the numbers. To get the sum, do this:
int sum = userInfo[0] + userInfo[1];
Also, even if your array had a third slot, you can only access individual elements by their numerical index (0, 1, or 2 in this case). Not by a String like result.
In java, arrays only have zero and positive integer indexes. This means that an array can only be accessed with 0 to size of the array minus 1.
If you want to do something like:
userInfo["result"] = userInfo[0] + userInfo[1];
You can try the following:
int result = userInfo[0] + userInfo[1];
System.out.println(result);
or:
Map<String,Intgeer> example = new HashMap<String,Intgeer>();
example.put("result", new Integer(userInfo[0] + userInfo[1]));
System.out.println(example.get("result"));
There are several problems here as I mentioned in comments. You declare an array of int here:
int userInfo[];
Then try to pass a string into it here (that won't work):
userInfo["result"]; // This is bad news
Your cleaned-up code should look like this:
int userInfo[];
userInfo = new int[2];
userInfo[0] = 11;
userInfo[1] = 20;
int sumArrayValues = userInfo[0] + userInfo[1];
System.out.println(sumArrayValues);
Happy coding!
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I am doing some experiments on my own about quantization processes etc.
I try to implement a binarization process which makes a "binary string" which will get processed by xor afterwards and some other stuff.
Anyhow the binarization is the following, where d and u are some numbers that will get compared:
String b = "";
for (int i = 0; i < u.length; u++) {
if(d[i] < u[i]) {
b[i] += '0';
} else {
b[i] += '1';
}
}
Currently like described I have a string where each character is 0 or 1.
Using a BigInteger gives me an Object where I can XOR two values against each other:
BigInteger bi = new BigInteger(b, 2);
(...)
BigInteger result = bi.xor(other_bi);
Is there another way to achieve what I want to do? I didn't find anything but maybe there is one I have not found?
The BitSet class is more appropriate for representing a sequence of bits. To set a bit you would use the BitSet.set method.
Taking your example as a BitSet.
BitSet bs = new BitSet(u.length);
for (int i = 0; i < u.length; u++)
if(d[i] >= u[i])
bs.set(i);
BitSet bs2 = ...
bs2.xor(bs); // changes and reuses bs2.
int bitsSet = bs2.cardinality();
int firstSetBit = bs2.nextSetBit(0);