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Questions tagged [loops]

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2
votes
5answers
571 views

Do recursive algorithms generally perform better than their for-loop counterpart?

I'm sure this is not a challenge for you but it remains an open question for me: Is it wise to prefer a recursive algorithm over its for-loop counterpart? E.g. take the evaluation of the natural ...
5
votes
4answers
1k views

Loops at low level

When programming with high level languages like Python or Matlab, it is always better to model the problem such as the solution is some kind of vector or matrix multiplication, to avoid loops. But ...
1
vote
1answer
370 views

Why are functional programs considered slower than procedural counterparts asymptotically, if the opposite appears true?

I've read and been told way too many times that functional algorithms and data structures have an obligatory O(log(N)) slowdown in respect to their procedural (for-...
3
votes
1answer
639 views

Running time function for an algorithm with while and for loop

I have trouble determining the running time function for algorithm below. I know that there are initially two assignment operations, int i=n and ...
1
vote
1answer
444 views

provability of while loop vs for loop [closed]

I'm abit afraid to ask this question here seeing as I asked it on programmers SE already, the thing is I think the question is more about the underlying theory than the use in practice (or call it ...
0
votes
1answer
521 views

Algorithm analysis of nested loop [duplicate]

so I have this code: for (int i=1; i < n; i=i*5) for (j=i; j < n; j++) sum = i+j; And I'm wondering, what's the time complexity of this for ...
2
votes
1answer
488 views

Simplifying a nested sum

I'm trying to analyze an algorithm of a function, I can express the function in term of summation, but I have no clues on how I could simplify this summation down to get the run-time in tern of big $O$...
0
votes
0answers
16 views

Runtime of this loop [duplicate]

I need some advice on how to determine the runtime of this loop : s=0 for ( i=1 , i <= 2^m ; i=i*2 ) { s++ } return s With $C_1$ = actions ...
-1
votes
1answer
163 views

What is the time complexity (big O) of this nested for-loop? [duplicate]

What is the time complexity (big O) of this nested for-loop? I believe it's either O(n) or O(n^2) ...
0
votes
1answer
644 views

Finding a Hoare logic correctness proof for a Repeat-Until loop

How can we prove a program in repeat until using Hoare Logic? I've found a rule like this: {P} S {R}, {R ^ ~B -> P}, {R ^ B -> Q} for ...
0
votes
0answers
17 views

Confusion with space and time usage [duplicate]

The following is my own set-up code: ...
1
vote
1answer
263 views

Big-O Time Complexity of nested for loops [duplicate]

My gut tells me the time-complexity of the following code is simply O(n^2). However, I'm not convinced, thinking it could possibly be O(n^3): ...
8
votes
2answers
305 views

How to bridge theory and implementation for while loops?

I'm working on my own little programming language for educational purposes, and I've run into a little bit of a problem. There are a few different solutions for it, but all of them seem inelegant - ...
-2
votes
1answer
529 views

Complexity Analysis for a nested loop with two methods [duplicate]

Hey I am studying for my intro algorithms class final and I'm not sure if I'm understanding this question correctly (its from a sample final exam). If someone could explain this to me that would be ...
0
votes
0answers
30 views

Nested Loop Complexity [duplicate]

I have several lists of varying size, each index of the list contains both a key and an object : list1.add('Key', obj). The lists are all sorted. My aim is to iterate through the list and match 1 or ...
1
vote
1answer
304 views

Loop invariant: decreasing a variable and swapping it

As an example exercise, we were asked to find the loop invariant for this bit of code. ...
-1
votes
1answer
2k views

Runtime of nested loops

What is the asymptotic runtime of fthe ollowing piece of code in terms of number of updates to S in worst case. ...
0
votes
0answers
18 views

Big o notation for the algo [duplicate]

Asked this at programmers Stack Exchange, was recommend to ask here : What would be the big o for the algo: for (i=0; i < n*n; i++) for(j=0; j<i*i; j++) ...
0
votes
1answer
194 views

Understanding the time-complexity of Insertion Sort

From my textbook, I am studying the time-complexity of the insertion sort algorithm (shown below). ...
1
vote
1answer
1k views

Explanation of the complexity of a loop [duplicate]

I am confused on the following: In the following trivial code: ...
2
votes
1answer
134 views

Nested loops: Still $\mathcal O(n)$?

I have an algorithm similar to this: i=1 while(i < n) { //something in O(1) while(i < n && cond) { //something in O(1) i++ } i++ } ...
0
votes
2answers
250 views

What is the Big O estimate of a nested for loop?

I am trying to figure out what the big o estimate of the following for loop is. ...
0
votes
0answers
42 views

Time complexity of complex nested for loops [duplicate]

What are the time complexities of the following code? I posted this on the general stackexchange website, but it was suggested that I post it here. ...
1
vote
0answers
121 views

Complexity of a nested for loop [duplicate]

I'm trying to work through various exercises in Skiena's "Algorithm Design Manual." One problem that I am stuck on is as follows: What value is returned by the following function? Express your ...
0
votes
3answers
758 views

Calculating time complexity of two interdependent nested for loops

Consider the following code segment : for (int i = 1; i <= n; i++ ) { for (int j = 1; j <= n; j = j + i ) { printf("Hi"); } } Here, the ...
1
vote
2answers
56 views

make Magic Square? [closed]

I need to write a function that takes in a 2D list, that is a NEARLY magic square, meaning that if you perform ONE swap, it becomes a magic square. The function would take in this nearly magic square, ...
1
vote
1answer
770 views
1
vote
1answer
1k views

Sum number of times statement is executed in triple nested loop

I have this code fragment: for( i=0; i<n; i++ ) for( j=0; j<i; j++ ) for( k=0; k<j; k++ ) S; I need to find the number of times ...
6
votes
3answers
14k views

What is the asymptotic runtime of this nested loop? [duplicate]

I am trying to analyse the runtime of this algorithm: for(i=1; i < n; i++){ for(j=1; j <= i; j++){ statement1; } } Expanding the ...
3
votes
1answer
757 views

Theta Runtime of Nested for Loops

I have two for loops, one nested within the other. I have two int variables n and U, where U > n. I know that the outer loop runs exactly U times (pretty much <...
1
vote
1answer
278 views

Can a Turing machine decide if a LOOP program stops for the integer input 0

This is a question I found in a practice exam while I am preparing for my mid term exam. The answer needs justification, either a pseudo code or a logical explanation why not. What puzzled me about ...
1
vote
1answer
430 views

Is it possible to write a universal loop program for if-then & loop programs and it is possible to write a universal while program for while progra

Is it possible to write a universal loop program for if-then & loop programs and it is possible to write a universal while program for while programs? Long version and some background: Before ...
0
votes
1answer
97 views

Confusion related to calculating time complexity

I have some confusion related to calculating the time complexity of this algorithm opt(i) for j=i:n a = f(i,j) + opt(j+1) end How is the running ...
4
votes
2answers
1k views

Analyzing programs with multiple for-loops

If they were all linked to make a condition such as ($1 < i < j < k < n$), I know how to solve, but the last loop is disconnected so I have no clue on how to do these... the ones like <...
4
votes
1answer
9k views

Triple nested for-loops [duplicate]

Possible Duplicate: A puzzle related to nested loops I am trying to count the exact/total number of iterations the following nested for-loops are executed: ...
0
votes
2answers
499 views

A puzzle related to nested loops

For a given input $N$, how many times does the enclosed statement executes? for $i$ in $1\ldots N$ loop $\quad$for $j$ in $1\ldots i$ loop $\quad$$\quad$for $k$ in $i\ldots j$ loop $\quad$$...
1
vote
2answers
2k views

Runtime analysis of a nested loop

I have some difficulties performing the worst case analysis on this algorithm. The outermost loop is executed $2N$ times. The while loop, in the worst case, will increase by $2$ each time, so it ...
1
vote
1answer
550 views

Asymptotic time complexity of a two-loop program

I have two pieces of code in a function which I'm trying to calculate the asymptotic running time for: ...
4
votes
2answers
9k views

Time complexity formula of nested loops

I've just begun this stage 2 Compsci paper on algorithms, and stuff like this is not my strong point. I've come across this in my lecture slides. ...
2
votes
1answer
3k views

Time complexity of a triple nested loop with squared indices

I have seen this function in past year exam paper. ...