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PORecursive Bubble Sort
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copied!<p>I am having some trouble with this. We basically have been asked to create two versions of a program that will sort an array of 50 items then display the largest numbers in LED's. I have got it working using a basic bubble sort and it displaying. My issue is when I have to do this using recursion. Unfortunately my knowledge on recursion is very limited as I missed the lecture on it -.- He has also not put the notes online. I have had a long google however still can't get my head around it. So I ask a few things. Firstly, could someone explain recursion in relation to a bubble sort using sedo code. Secondly, am I completely wrong with my attempt.</p> <pre><code>int numbers[49]; void setup() { pinMode(12, OUTPUT); pinMode(11, OUTPUT); pinMode(10, OUTPUT); pinMode(9, OUTPUT); pinMode(8, OUTPUT); pinMode(7, OUTPUT); pinMode(6, OUTPUT); pinMode(5, OUTPUT); Serial.begin(9600); } void loop() { resetLEDLow(); genNumbers(); sortNumbers(); displayNumber(); delay(5000); } void resetLEDLow() { digitalWrite(12, LOW); digitalWrite(11, LOW); digitalWrite(10, LOW); digitalWrite(9, LOW); digitalWrite(8, LOW); digitalWrite(7, LOW); digitalWrite(6, LOW); digitalWrite(5, LOW); } void genNumbers() { for( int i = 0 ; i < 50 ; i++ ) { numbers[i] = random(256); } } void sortNumbers() { int sizeOfArray = sizeof(numbers)/sizeof(int); int check = 1; if( check != 0 ) { check = 0; for( int i = 0 ; i < sizeOfArray ; i++ ) { for ( int j = 1 ; j < sizeOfArray ; j++ ) { if( numbers[j-1] > numbers[j] ) { int temp = numbers[j-1]; numbers[j-1] = numbers[j]; numbers[j] = temp; check++; } } } sortNumbers(); } } void displayNumber() { int i = 12; int a = numbers[49]; Serial.println(numbers[49]); while ( a > 0 ) { int num = a % 2; a = a / 2; if( num == 1 ) { digitalWrite(i, HIGH); }else{ digitalWrite(i, LOW); } i--; } } </code></pre> <p>I know that code does not work as when it loops round count is reset to 1 so the condition will never be true thus meaning it will loop round forever and ever. So, what do I need to change or is what I am doing not really recursion at all?</p> <p>Really need some help with this, got my brain going round and around.</p> <p>Edit: Here is my attempt with the new recursion. I have removed code not relevant to the problem.</p> <pre><code>void loop() { int topLevel = 0; int currentSort = 0; int sizeOfArray = sizeof(numbers)/sizeof(int); int numbers[49]; sortNumbers(topLevel,currentSort,sizeOfArray,numbers); } int sortNumbers(p,c,l,numbers) { // Swap if they are in the wrong order if( numbers[c-1] > numbers[c] ) { int temp = numbers[c-1]; numbers[c-1] = numbers[c]; numbers[c] = temp; } // If we have finished this level and need to go to next level if( c == l ) { c = 0; p++; } // Finished if( p == l+1 ) { return numbers; } // Continue to the next place return sortNumbers(p,c+1,l, numbers); } </code></pre> <blockquote> <p>Sort50Rec:-1: error: 'p' was not declared in this scope Sort50Rec:-1: error: 'c' was not declared in this scope Sort50Rec:-1: error: 'l' was not declared in this scope Sort50Rec:-1: error: 'numbers' was not declared in this scope Sort50Rec:-1: error: initializer expression list treated as compound expression Sort50Rec.cpp: In function 'void loop()': Sort50Rec:19: error: 'numbers' was not declared in this scope Sort50Rec:21: error: 'sortNumbers' cannot be used as a function Sort50Rec.cpp: In function 'void genNumbers()': Sort50Rec:42: error: 'numbers' was not declared in this scope Sort50Rec.cpp: At global scope: Sort50Rec:46: error: redefinition of 'int sortNumbers' Sort50Rec:-1: error: 'int sortNumbers' previously defined here Sort50Rec:46: error: 'p' was not declared in this scope Sort50Rec:46: error: 'c' was not declared in this scope Sort50Rec:46: error: 'l' was not declared in this scope Sort50Rec:46: error: 'numbers' was not declared in this scope</p> </blockquote> <p>I am sure part of it is the way I am naming my function and am I right in thinking you can only return one value? Or not?</p> <p>Edit: Fixed error pointed out new error.</p> <pre><code> void loop() { int topLevel = 0; int currentSort = 0; int numbers [49]; int sizeOfArray = sizeof(numbers)/sizeof(int); numbers = sortNumbers(topLevel,currentSort,sizeOfArray,numbers); } int sortNumbers(int p,int c,int l,int numbers) { // Swap if they are in the wrong order if( numbers[c-1] > numbers[c] ) { int temp = numbers[c-1]; numbers[c-1] = numbers[c]; numbers[c] = temp; } // If we have finished this level and need to go to next level if( c == l ) { c = 0; p++; } // Finished if( p == l+1 ) { return numbers; } // Continue to the next place return sortNumbers(p,c+1,l, numbers); } </code></pre> <blockquote> <p>Sort50Rec.cpp: In function 'void loop()': Sort50Rec:19: error: invalid conversion from 'int*' to 'int' Sort50Rec:19: error: initializing argument 4 of 'int sortNumbers(int, int, int, int)' Sort50Rec:19: error: incompatible types in assignment of 'int' to 'int [49]' Sort50Rec.cpp: In function 'void genNumbers()': Sort50Rec:40: error: 'numbers' was not declared in this scope Sort50Rec.cpp: In function 'int sortNumbers(int, int, int, int)': Sort50Rec:47: error: invalid types 'int[int]' for array subscript Sort50Rec:47: error: invalid types 'int[int]' for array subscript Sort50Rec:49: error: invalid types 'int[int]' for array subscript Sort50Rec:50: error: invalid types 'int[int]' for array subscript Sort50Rec:50: error: invalid types 'int[int]' for array subscript Sort50Rec:51: error: invalid types 'int[int]' for array subscript Sort50Rec.cpp: In function 'void displayNumber()': Sort50Rec:71: error: 'numbers' was not declared in this scope</p> </blockquote> <p>Thanks</p>

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