# Questions tagged [binary-search]

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### when to search in binary search right, when left?

in the binary search algorithm: If no items Return false If middle item is 50 Return true Else if 50 < middle item Search left half Else if 50 > middle item Search right half like can we do the ...
149 views

### Purpose of sizeof(book)/sizeof(string) in lectures' binary sort?

string book[] = { "Chen", "Kernighan", "Leitner", "Lewis", "Malan", "Muller", "Seltzer", "Shieber", "Smith" } int main(...
24 views

### Code won't progress unless user inputs a number

I was writing a binary search function before finishing lecture 3 because I wanted to do some practice on my own. I was using scanf, which I had looked up, as I wanted to learn how to code without the ...
32 views

### find problem with my code - CPU overload

I cannot figure out what is wrong with my code. /** * Returns true if value is in array of n values, else false. */ bool search(int value, int values[], int n) { // ensures that the n is non ...
96 views

### pset3 find less comfortable if else expression result unused

I do not understand why I get an errors: error: expected ';' after expression else (value > values[l]) and helpers.c:40:21: error: expression result unused [-Werror,-Wunused-value] ...
48 views

### CS 50 - pset3 find helpers: Why do binary search and selection short not work?

the command line yells at me but I cannot find out why. Any ideas what could be wrong? Here is my code: /** * helpers.c * * Helper functions for Problem Set 3. */ include include "helpers.h" /...
241 views

### PSET3 find having trouble. Can someone help?

For some reason bubble sort is not working. Can someone help. binary search bool search (int target, int array[],int length) { int end = length-1; int start = 0; while (array[start] < ...
71 views

### pset3: sort and search work in separate files, but my helpers.c doesn't work

I dealt with sorting in a separate file first, and then I dealt with searching in another file. They seem to work okay or at least worked for the numbers I feed in, but when I put them in helpers and ...
26 views

### For pset3 binary search will this code work?

Here is the code . bool binary_search (int target, int array[],int length) { int end = length-1; int start = 0; while ( array[end_num]- array[start_num] > 0) { ...
34 views

### do I need recurson for binary search?

Also do I need recursion for any of the pset3 solutions? If yes any good sources on recursion. There was a quick example in lecture 3. Will that suffice? Preferably a video. I realize I could just ...
59 views

### Find.c - Binary Search probable integer overflow

Here's the gist: https://gist.github.com/Securiteru/a83e4f1a028acd0b1013def793b5dcdc And the output: ... 60697 61151 61190 61275 61460 61608 61618 61746 61750 61822 62111 62178 62183 62311 62448 ...
417 views

### Pset3, Find, search

In "Find" problem, something seems wrong with my binary search Algorithm, because in check50, helpers.c wouldn't compile, I tried to compile it, then it gave me this weird error: clang -fsanitize=...
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### pset 3 binary search help

I am working on pset 3 for cs50 on edx, and I'm having quite a bit of trouble with the binary search problem. My program worked fine when I tested it with a linear search (so I think the problem isn'...
107 views

### PSET3 Binary Search Function Infinite Loop

When I try running find.c inputting: ./generate 1000 50 | ./find 127 it should return that the value (127) was found, however when I do it with my code, it seems to create an infinite loop. Also, ...
187 views

### Pset3 helpers.c

i'm stuck in binary search. Check50 doesn't pass all the checks and it doesn't find the needle, I feel like the algorithm i have implemented is correct but it doesn't work. I've been stuck in this for ...
126 views

### Binary Search for helpers.c

so as the title suggests I am having some trouble with my implementation of binary search. So based on the logic shown in the lecture, I think my implementation is fine, indeed it works for the cases ...
103 views

### Binary Search Pset 3 help

As my question is titled, I would appreciate help with my binary search, shown below. Currently, the search will always return false. I am almost certain that my sorting algorithm is correct, as it ...
158 views

### Segmentation Fault pset3 for Find

I'm getting a segmentation fault error and I can't figure out why. void sort(int values[], int n) { // TODO: implement a sorting algorithm for (int i = 0; i<n; i++) { if ((n!=i+...
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### Result doesn't match expected output

I just finished the helpers.c pset, where you have to implement a counting sort and then a binary search. I havent made it recursive yet but it works in all of my own test cases. I also ran the ./...
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### pset3: search (am I in the right track??)

bool search(int value, int values[], int n) //search for middle lists if (value == values [n / 2]) { return 1; } //number greater search left else if ( value > values[n / 2 ]) { search(int ...
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### Pset 3 Recursive Binary Search problems - Always returns true

I have tried almost everything and edited my code a hundred times in search of an answer. It seems that whenever I run the program (find.c) the result always resolves to true. Not sure where the ...
17k views

https://www.youtube.com/watch?v=5xlIPT1FRcA&t=200s I am struggling to understand how to implement binary search. According to the video, there are 14 numbers in the array. Then he goes on to ...
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### cs50x pset3 find - Need help with the counting sort

can someone please look at my code and tell me where I went wrong with my counting sort algorithm (Or binary search algorithm, if that's where the problem lies...?). Please and thank you. Binary ...
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### C: Binary Search searches and finds but incorrect exit code

This code is finding all the numbers correctly. Only problem is it's throwing error of "\ expected an exit code of 1, not 0" when the number is not present. Help would be appreciated. bool search(int ...
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### Advice re: Binary search - various issues

I need advice as to what to change in this code to make it work. I am new at this so I need specifics, please. Please, no opinions on whether it's trash or what mark you would give if grading it. That ...
36 views

### C: Pset 3: Binary Search - 'expected an exit code of 0, not 1' (not finding n)

This is an attempt at binary search. n is the user input (from main script). This code compiles but doesn't find the needle in the haystack. I'm a bit lost and would welcome assistance. bool ...
49 views

for some reason this binary search code keeps returning true, when providing the haystack from generate.c, even if the "needle" isnt there. when manually inputing the haystack, the code runs perfectly....
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### Pset 3: Find (more comfortable) - child exited with status 255 & exits with wrong code

I ambitiously decided to try the more comfortable version of this task, although I'm very much "less comfortable" with regard to any computer skills... Before I give up, I'd like to ask you what's ...
214 views

### PSET3 \ expected an exit code of 0, not 1 (find.c)

I successfully built my program and went on to check it using check50 only to discover this :) helpers.c exists :) helpers.c compiles :) finds 42 in {42,43,44} :) finds 42 in {41,42,43} :) finds 42 ...
94 views

### Pset3 Find - Not sure what is wrong with helpers.c code

I am not sure what is wrong with the code. It seems to work on some of the criteria when using cs50's check50, but does not work on others. There also does not seem to have a pattern about the wrong ...
37 views

### Recursive function problem - return value

I am getting the following error below. It has to do with my binarySearch function. helpers.c:149:1: error: control may reach end of non-void function [-Werror,-Wreturn-type] } ^ However I have a ...
48 views

### Pset3 helpers.c while loop exiting unexpectedly

I am trying to implement a binary search algorithm. However, my while loop isn't working as expected. Having used printf and debug50 with a list of 100 numbers, it seems that the while loop only gets ...
100 views

### Binary Search pset3

bool search(int value, int values[], int n) { int found = 0; int notfound = 0; int minindex = 0; int maxindex = n; int midindex = 0; do { midindex = (minindex + maxindex) / 2; if (minindex &...
334 views

### PSet 3, binary search implementation

I'm struggling with implementation of binary search in PSet 3, and my code can't quite get past check50. Here's my code: bool search(int value, int values[], int n) { // TODO: implement a ...
163 views

### helpers.c passes check50 but fails ./generate 1000 50 | ./find 128

check50 gives me all smiles, but when I run the test code ./generate 1000 50 | ./find 127 or 128 they both return "Found needle in haystack". How is that possible? And also, can I be sure my code is ...
41 views

### pset3 binary search , shows errors in check50

i don't understand acc. to the algorithm it should work correctly , but it doesn't
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### pset3 binary search , problems with check50

i have tried a lot but cannot find the meaning of the last two errors of check50 please help
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### pset3: When testing binary search code, how do I print when needle is found?

I would like to test if my binary search function is working correctly. I have created an array that is passed into a working bubble sort function. Printing the sorted array works just fine, all I ...
78 views

### Pset3 recursive binary search function - check50 gives me four :( and I don't know why

I would be really grateful if someone could offer me a hint as to where I'm going wrong with this - I've been stuck for a couple of days now. When I work through the code step by step on paper it ...
51 views

### binary search algorithm

Many sources say that you need to put "int l = n" the element next to last instead of "int l = n - 1"(int f = 0; int l = n - 1; int mid;) in my example. I am not sure why? Moreover it seems my code ...
44 views

### return -1 does not end function execution

This is my code. 65 int BinarySearch(int key, int array[], int min, int max) 66 { 67 int mid; 68 69 if (max < min) 70 { 71 return -1; 72 } 73 else 74 ...
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### How do I set a pointer to access the left half of an array? [PSET 3 - Binary search]

I'm having trouble accessing only the left half of an array, doing the same for the right half works fine for now, at least I'm not getting any errors. I figured accessing the array using pointers ...
178 views

### Segmentation fault in find.c

I've been working on find.c for a long time now and I've managed to get to the point where it will return the correct output when the needle is in the haystack, but when it isn't I get a segmentation ...
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### find.c compiles but fails check50 - I believe binary search is to blame

Why does my code fail check50? This is the code of my binary search. I know it's buggy, and I spent the last hours reading answers to similar questions, the information I found doesn't quite cut it ...
98 views

### Check50 is claiming that it's recieving an exit code of 0 rather than 1 (different scenario)

I know this question has been answered before (pset 3 "search": expected an exit code of 0, not 1), but I took a look at it, and it seems that the scenario in which the person asked the ...
259 views

### Stuck in loop on Binary Search

I have some problems with my Binary search and would greatly apprecaite help in this. I've debugged it and it seems that my "mid" variable doesn't change. As such, if "value" doesn't equal value[mid] ...
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### binary search pset 3 pointer to integer error

I am trying my hands on binary search. I get those pointer to integer errors :( Can sonmeone more experience give me a hand ? bool search(int value, int values[], int n) { int first=0; int last=n-1; ...
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### Binary search: always false when 2 or 3 numbers entered

My binary search works correctly when you enter 1,4,5,6,7 (etc)... numbers or 'haystacks'. However, when 2 or 3 numbers or 'haystacks' are entered, false is always returned. I have tried everything I ...