I was wonder how you would go about exiting a method early. If this was a void type, I would just do "return", however since this is an int type, it wants me to return an integer. How do I return to main without returning any integers. Thanks.
public static int binarysearch(String[] myArray, String target, int first, int last)
{
int index;
if (first > last)
{
index = -1;
System.out.println("That is not in the array");
// Return to main here
}
You can't return from a method without a return value, in the traditional sense.
You can either return -1; and declare in your documentation that -1 represents a failed search, or you can throw an exception. If you throw an exception, though, you'll need to catch it. You can read more about that in the linked article.
A couple of options....
1. break;
2. return a value that you know would not be returned from a valid result. Eg 99999999 or -34
Those would be simple choices....
Edit
Of course break would only exit the loop. So youd still need to return a known value.
Related
It says there is no suitable entry point for the program as well as invalid expression of int when attempting to use the printMenu method. My instructions specify that I need to initialize the array and menu in the main and utilize the 5 methods in a switch statement but I am tripping over the Main method. I am unable to understand how to reference an (int[] args) with a string. I was able to do it just fine with a switch statement but since moving onto methods I have struggled understanding how to reference properly and would appreciate any tops or fixes on how to adjust.
public static void Main(string[] args)
{
int[] initArray = new int[10];
Console.Write("Would you like to: \n1) Enter a number\n2)Print the array \n3)find the sum of the array\n4)Reset the array\n5)Quit\n");
int input = Convert.ToInt32(Console.ReadLine());
printMenu(int[input]);
}
public void printMenu(int[] args)
{
Console.Write("Would you like to: \n1) Enter a number\n2)Print the array \n3)find the sum of the array\n4)Reset the array\n5)Quit\n");
int input = Convert.ToInt32(Console.ReadLine());
do
{
switch (input)
{
case 1:
enterNum(args);
break;
}
} while (input < 5);
}
You can call the printMenu method like this:
printMenu(new int[]{ input });
If you have a second input you would do:
printMenu(new int[]{ input, input2 });
Using an array of integers is only logical when you want to pass in multiple integers. When you are never going to pass in more than 1 ints I suggest changing the signature of printMenu to ask for just one integer: printMenu(int arg) and just pass in the one input.
printMenu(input);
I am trying to make the producer-consumer method using c++11 concurrency. The wait method for the condition_variable class has a predicate as second argument, so I thought of using a lambda function:
struct LimitedBuffer {
int* buffer, size, front, back, count;
std::mutex lock;
std::condition_variable not_full;
std::condition_variable not_empty;
LimitedBuffer(int size) : size(size), front(0), back(0), count(0) {
buffer = new int[size];
}
~LimitedBuffer() {
delete[] buffer;
}
void add(int data) {
std::unique_lock<std::mutex> l(lock);
not_full.wait(l, [&count, &size]() {
return count != size;
});
buffer[back] = data;
back = (back+1)%size;
++count;
not_empty.notify_one();
}
int extract() {
std::unique_lock<std::mutex> l(lock);
not_empty.wait(l, [&count]() {
return count != 0;
});
int result = buffer[front];
front = (front+1)%size;
--count;
not_full.notify_one();
return result;
}
};
But I am getting this error:
[Error] capture of non-variable 'LimitedBuffer::count'
I don't really know much about c++11 and lambda functions so I found out that class members can't be captured by value. By value though, I am capturing them by reference, but it seems like it's the same thing.
In a display of brilliance I stored the struct members values in local variables and used them in the lambda function, and it worked! ... or not:
int ct = count, sz = size;
not_full.wait(l, [&ct, &sz]() {
return ct != sz;
});
Obviously I was destroying the whole point of the wait function by using local variables since the value is assigned once and the fun part is checking the member variables which may, should and will change. Silly me.
So, what are my choices? Is there any way I can make the wait method do what it has to do, using the member variables? Or I am forced to not use lambda functions so I'd have to declare auxiliary functions to do the work?
I don't really get why I can't use members variables in lambda functions, but since the masters of the universe dessigned lamba functions for c++11 this way, there must be some good reason.
count is a member variable. Member variables can not be captured directly. Instead, you can capture this to achieve the same effect:
not_full.wait(l, [this] { return count != size; });
I have the following method:
From what I learned methods which are not voids need a return. For the following examples I can see two returns, once after if(), and one at the end.
For this example if String s is not a digit it will return the boolean as false. Which makes sense. If it is a digit then it will check whether it is in the interval. I guess I am confused regarding whether we can have multiple returns in such cases and what the limitations are, if there are any. thank you.
private boolean ElementBienFormat(String s) {
for (int i = 0; i < s.length(); i++) {
if (!Character.isDigit(s.charAt(i))) {
return false;
}
}
int n = Integer.valueOf(s);
return (n>=0 && n <=255);
A method will "quit" (return) when control reaches a return. So in this case as soon as a character is not a digit in the input String control will go back to the caller (with the appropriate value).
boolean success = ElementBienFormat( "a" ); // <-- control would go back here with the value of false.
Another quick note is that a void method can have multiple return statements as well
private void Method( int n )
{
if( n < 0 )
return;
//...
//implicit
//return;
}
I can't figure this interview question.
You have an array of integers. You need to provide another Data structure that will have these functions:
int get(int index)
void set (int index, int value)
void setall(int value)
They all do what you guess they're suppose to do.
The limitation is that every function is in O(1).
How can you design it so that setAll will be O(1).
I thought about adding another field to each integer, that will point to an integer that will be changed every time setAll is called. the problem comes when someone call setAll and then set then get.
Edit: I changed the names of the variables so it would be clearer. Also, since you asked, get is suppose to return array[i], set(index, value) suppose to put the value value in array[index].
After setall(index, value) you should get (get(i) == get(j) == value) for every i,j in the array.
How about storing a "version number" with each variable, i.e.
int globalValue, globalVersion;
int nextVersion;
int[] localValue, localVersion;
int get(int i) {
if (localVersion[i] > globalVersion)
return localValue[i];
else
return globalValue;
}
void set(int i, int value) {
localValue[i] = value;
localVersion[i] = nextVersion++;
}
void setAll(int value) {
globalValue = value;
globalVersion = nextVersion++;
}
Keep a DateTime field ( or simply a counter ) with each element in the array, a setAllValue variable and setAllDateTime variable. With each set, update the DateTime/counter of the element. With SetAll, update the value and DateTime of setAllDateTime.
In get, compare the DateTime of SetAll with DateTime of the element, whichever is newer, return that.
Why does the following code throw an exception when getting to the second scanf_s after entering an number to put into the struct.
This by no means represents a complete linked list implementation.
Not sure how to get onto the next scanf_s when having entered the value? Any ideas?
EDIT: Updated code with suggested solution, but still get an AccessViolationException after first scanf_s
Code:
struct node
{
char name[20];
int age;
float height;
node *nxt;
};
int FillInLinkedList(node* temp)
{
int result;
temp = new node;
printf("Please enter name of the person");
result = scanf_s("%s", temp->name);
printf("Please enter persons age");
result = scanf_s("%d", &temp->age); // Exception here...
printf("Please enter persons height");
result = scanf_s("%f", &temp->height);
temp->nxt = NULL;
if (result >0)
return 1;
else return 0;
}
// calling code
int main(array<System::String ^> ^args)
{
node temp;
FillInLinkedList(&temp);
...
You are using scanf_s with incorrect parameters. Take a look at the examples in the MSDN documentation for the function. It requires that you pass in the size of the buffer after the buffer for all string or character parameters. So
result = scanf_s("%s", temp->name);
should be:
result = scanf_s("%s", temp->name, 20);
The first call to scanf_s is reading garbage off the stack because it is looking for another parameter and possibly corrupting memory.
There is no compiler error because scanf_s uses a variable argument list - the function doesn't have a fixed number of parameters so the compiler has no idea what scanf_s is expecting.
You need
result = scanf_s("%d", &temp->age);
and
result = scanf_s("%f", &temp->height);
Reason is that sscanf (and friends) requires a pointer to the output variable so it can store the result there.
BTW, you have a similar problem with the parameter temp of your function. Since you're changing the pointer (and not just the contents of what it points to), you need to pass a double pointer so that the changes will be visible outside your function:
int FillInLinkedList(node** temp)
And then of course you'll have to make the necessary changes inside the function.
scanf() stores data into variables, so you need to pass the address of the variable (or its pointer)Example:
char string[10];
int n;
scanf("%s", string); //string actually points to address of
//first element of string array
scanf("%d", &n); // &n is the address of the variable 'n'
%19c should be %s
temp->age should be &temp-age
temp->height should be &temp->height
Your compiler should be warning you
about these errors
I believe you need to pass parameters to scanf() functions by address. i.e. &temp->age
otherwise temp-age will be interpreted as a pointer, which will most likely crash your program.