Homework Help v1.3

[Keerua]

Try google books

[Jeaxz]

Originally Posted by Keerua

Try google books

They don't give the full book... :( and they're pretty limited to what they can offer.

[Keerua]

That is because the book isn't free will be hard to find an ebook version, if there is even one, which I doubt there is or google would have returned a pdf or two.

[Tammy]

Try searching torrent sites for ebooks. I've managed to find some books that were useful.

[Batr]

Originally Posted by Soul Fang

Select all true statements from the following:
a. Metals are good conductors of electricity, but not of heat.
b. The oxides of nonmetals form acidic solutions when dissolved in water, or - if they are not soluble - will dissolve in basic aqueous solution.
c. Only metals have high electrical conductivity.
d. Not all nonmetal atoms release energy when forming a 1- anion.

i know a is false for sure, and that d is true. But not sure about b and c. any help appreciated.

I'm not sure about b, but for c, there are some ceramics with high electrical conductivity

[Ice(v)an]

C++

Part 1 (%60)

You need to read infix expressions from the input infixFile (one expression per line) and produce the corresponding postfix expressions that you will save in file postfixFile. An example of an infix expression is the following:

(12 + 3) * ( 9 – 74) + 34 / ((85 – 93) +(3 + 5) * 3) - 5

You have to parse this expression from left to right, identify the operands, the operators and the parentheses and ignore blanks. You will implement the infix to postfix conversion algorithm using a stack of operators and parentheses. You can use any stack implementation (i.e. array, linked-list, list, or STL).

You should be able to handle syntactically wrong infix expressions using exceptions. In this case you should output a message on the postfixFile indicating the type of error (i.e. “missing right parenthesis”).

Part 2 (%40)

Now you need to evaluate each postfix expression using the stack algorithm described in class and place the results in the file resultFile.

----------------------------



#include <iostream>
#include <stack>
#include <vector>
#include <sstream>
#include <string>
using namespace std;


int main()
{
int resultFile;

stack <string> op;
vector<string> postfix;
stack<int> number;

string line,str;



int evaluate_postfix(vector<string>& post,stack<int>& num1);

int precedence(string str1);
getline(cin,line);
istringstream iss(line);

while(!iss.eof())
{
iss>>str;
if(str=="+"||str=="-"||str=="*"||str=="/") // choose the operation
{

while(!op.empty()&&op.top()!="("&&precedence(str)> =precedence(op.top()))
{
postfix.push_back(op.top());
op.pop();
}// end while

op.push(str);
}// end if

else if(str=="(")
{
op.push(str);
}
else if(str==")")
{
while(op.top()!="(")
{
postfix.push_back(op.top());
op.pop();
}
op.pop();
}
else
{
postfix.push_back(str);
}

}// End While

while(!op.empty())
{
postfix.push_back(op.top());
op.pop();
}



resultFile=evaluate_postfix(postfix,number);

cout<< " The result is: " << resultFile << endl;

system("PAUSE");

return 0;
}// end Main



int precedence(string str)
{
if(str=="+"||str=="-")
return 1;
else if(str=="*"||str=="/")
return 2;
else
return 0;
}


/*
To evaluate Postfix we push any number onto the stack and tehn
pop the last two numbers from the stack and apply the operand to them.
*/


int evaluate_postfix(vector<string>& postfix,stack<int>& num)
{
for(vector<string>::const_iterator ptr=postfix.begin();ptr!=postfix.end();++ptr)
{

if(*ptr!="+"||*ptr!="-"||*ptr!="*"||*ptr!="/")
{
int number;
istringstream stm;
stm.str(*ptr);
stm>>number;


num.push(number);
}
else
{
int arg2=num.top();
num.pop();
int arg1=num.top();
num.pop();
int result;

if(*ptr=="+")
result=arg1+arg2;
else if(*ptr=="-")
result=arg1-arg2;
else if(*ptr=="*")
result=arg1*arg2;
else
result=arg1/arg2;
num.push(result);
}
}

int i=num.top();
num.pop();
return i;
}





Am I doing it right?

[Ice(v)an]

How come when I compile this I enter an infix expression and when I evaluate it I get crazy numbers.

[Danzer-]

Calculus Problem:

A swimming pool is 60 ft. long by 30 ft. wide. Water is being pumped into the pool at 600 ft3/min. How fast is the depth of the water changing at the moment the depth is 3 ft? 6 ft? 7 ft?

Vertical Cross-Sectional slice:
 

any help will be appreciated.

[o({})o]

Originally Posted by Danzer-

Calculus Problem:

A swimming pool is 60 ft. long by 30 ft. wide. Water is being pumped into the pool at 600 ft3/min. How fast is the depth of the water changing at the moment the depth is 3 ft? 6 ft? 7 ft?

Vertical Cross-Sectional slice:
 

any help will be appreciated.

This looks like a problem that will require at least two separate equations for depth of water at a certain time. I'd make one equation for when the water is still rising out of the lower basin, and then one equation for when it hits the main portion of the pool (rises out of the sloped part).

[Danzer-]

Originally Posted by o({})o

This looks like a problem that will require at least two separate equations for depth of water at a certain time. I'd make one equation for when the water is still rising out of the lower basin, and then one equation for when it hits the main portion of the pool (rises out of the sloped part).

Thanks,
I got the part a, when the depth is 3 ft.

V = (1/2)hw(b1+b2)
Then i plugged in the numbers:

600 = (1/2)h(30)(30+10)
and found dh/dt to be 4/5 or .8 ft/min at 3ft.

I'm stuck on the last two problems, when the depth is 6 and 7 feet.

[Keerua]

Solve x' - x^2 = 1 given x(0) = 1

It says it is seperable but I still can't understand how the fuck I am supposed to solve it, I was sick the day they lectured on that.... and I don't like the idea of seperating x from x...

I just took a shot and guessed arctan x + pi ?

[Tammy]

Originally Posted by Keerua

Solve x' - x^2 = 1 given x(0) = 1

It says it is seperable but I still can't understand how the fuck I am supposed to solve it, I was sick the day they lectured on that.... and I don't like the idea of seperating x from x...

I just took a shot and guessed arctan x + pi ?

Is this calculus?

x' can also be written as dx/dy then seperate y to one side and x to the other side

god I hope I'm not giving incorrect advice LOL

[Keerua]

Yeah

I used eulers to approximate it and apparently arctan x + C is the inverse function

so x(t) = tan (t + C)
and given the starting conditions

x(t) = tan(t + 0.25pi)

[Danny]

Dear Krozar,
Halp.

I know you're in love with Poli Sci, and I'm writing a paper for it.

Was wondering if you had any tips/info/insight on this question

"Do you see evidence of your representative engaging in the types of public relations efforts that are part of “governing by campaigning”? In general, do you think members of Congress engage in more or less of these behaviors than presidents? Why?"

I'm writing mine on Danny K. Davis from Illinois. I don't want you to do research for me and give me all the answers, I was just wondering what the question meant by, "Governing by campaigning."

Thanks

[Ice(v)an]

can someone help me with this?


Theory Problem (20 points)
(a) A sorting algorithm is stable if duplicates retain their relative positions in the sorted
sequence. For example, consider the following list of names:
George Bush
Al Gore
Hillary Clinton
Ronald Reagan
Rick Lazio
George W. Bush
Ralph Nader

If this list is sorted by last name only, then a stable sort will
produce this list:
George Bush
George W. Bush
Hillary Clinton
Al Gore
Rick Lazio
Ralph Nader
Ronald Reagan

whereas an unstable sort might produce this list:
George W. Bush
George Bush
Hillary Clinton
Al Gore
Rick Lazio
Ralph Nader
Ronald Reagan

Which of the following sorts is stable: insertion sort, bubble sort, mergesort, quicksort?
For each one, describe why it is or is not stable.


(b) The preorder traversal of a binary tree is "A B C D E F G H I" and inorder traversal
is "C D E B F A I H G". Draw the tree.

[Puree]

This is for a project...

For example:
"It is better to be yourself than to be like everybody else."

What others can you think of?

[The stig]

^It would be better to know exactly what but whatever.

"It's better to have loved and lost than to have never loved at all"

"Rules are merely guidelines for wise men" (not to sure if this is the exact wording)

"The best way to get over someone is to get unde rsomeone" (haha, couldn't resist)

That's all i can think of in my tired state, the first two are legit, hope this short post helps.

EDIT: I remembered one from a poem i read in school in year 11 (2 years ago, near on 3, wow)

"Why run when you can walk?"

[Ice(v)an]

1. (12 points) DEREG AIRLINES uses the table below to find out what flights to
take to get from one city to another.
To city 1 To city 2 To city 3 To city 4 To city 5
From city 1 - - 305 278 -
From city 2 101 - 234 176 -
From city 3 076 005 - - -
From city 4 432 901 675 - 765
From city 5 - 211 303 180 -

The table says that there is no direct service from city 1 to cities 2 and 5, direct
service from city 1 to city 3 on flight 305, direct service from city 1 to city 4 on flight
278 and so on. Travel between two cities can also be indirect. For example, to go
from city 1 to city 5 we can take flight 278 to city 4 and the flight 765 to city 5. You
have been hired by DEREG to help create a program that takes as input two city
numbers and prints out what flight or series of flights link two cities.
a. (3 points) Describe a C++ data structure you would use to store the table
above.

b. (6 points) Write a recursive function in C++
bool findroute(int from, int to, int flight[], int &size)
that will return in the array flight the flight number or numbers that link two
cities or an empty array if there is no path between them (size is the number of
elements in the array). The function returns true if a path is found and false
otherwise.

(pseudo-code)


c. (3 points) Discuss (DO NOT WRITE CODE) how you might modify or
change your data structure in part a) to allow for more than one flight
between cities.


::edit::

Gah, the table is messed up

[Yedi]

We have a ordinary differential equation which is defined as: dx/dt + x^2 = x, solve it.

I got so far as to get x(1-x)=e^c*e^t but how do I continue from there? I noticed there was some sort of 0 formula but I didn't get it.

[XandorXerxes]

Originally Posted by Danny

Dear Krozar,
Halp.

I know you're in love with Poli Sci, and I'm writing a paper for it.

Was wondering if you had any tips/info/insight on this question

"Do you see evidence of your representative engaging in the types of public relations efforts that are part of “governing by campaigning”? In general, do you think members of Congress engage in more or less of these behaviors than presidents? Why?"

I'm writing mine on Danny K. Davis from Illinois. I don't want you to do research for me and give me all the answers, I was just wondering what the question meant by, "Governing by campaigning."

Thanks

I don't know if you still need a hand with this, but my best guess would be that "governing by campaigning" refers to politicians looking to get on peoples' good sides instead of doing what's needed to be done. Governing by polls, or the politician's attempts to raise his or her perspective outlook in them.