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2D Array Chessboard Pattern

0 likes • Nov 18, 2022
C++
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Heapify a vector

CodeCatch
0 likes • Nov 19, 2022
C++
#include <iostream>
#include <vector>
using namespace std;
void swap(int *a, int *b)
{
int temp = *b;
*b = *a;
*a = temp;
}
void heapify(vector<int> &hT, int i)
{
int size = hT.size();
int largest = i;
int l = 2 * i + 1;
int r = 2 * i + 2;
if (l < size && hT[l] > hT[largest])
largest = l;
if (r < size && hT[r] > hT[largest])
largest = r;
if (largest != i)
{
swap(&hT[i], &hT[largest]);
heapify(hT, largest);
}
}
void insert(vector<int> &hT, int newNum)
{
int size = hT.size();
if (size == 0)
{
hT.push_back(newNum);
}
else
{
hT.push_back(newNum);
for (int i = size / 2 - 1; i >= 0; i--)
{
heapify(hT, i);
}
}
}
void deleteNode(vector<int> &hT, int num)
{
int size = hT.size();
int i;
for (i = 0; i < size; i++)
{
if (num == hT[i])
break;
}
swap(&hT[i], &hT[size - 1]);
hT.pop_back();
for (int i = size / 2 - 1; i >= 0; i--)
{
heapify(hT, i);
}
}
void printArray(vector<int> &hT)
{
for (int i = 0; i < hT.size(); ++i)
cout << hT[i] << " ";
cout << "\n";
}
int main()
{
vector<int> heapTree;
insert(heapTree, 3);
insert(heapTree, 4);
insert(heapTree, 9);
insert(heapTree, 5);
insert(heapTree, 2);
cout << "Max-Heap array: ";
printArray(heapTree);
deleteNode(heapTree, 4);
cout << "After deleting an element: ";
printArray(heapTree);
}

Daily: Find missing array value

aedrarian
0 likes • Dec 24, 2021
C++
/*
Good morning! Here's your coding interview problem for today.
This problem was asked by Stripe.
Given an array of integers, find the first missing positive integer in linear time and constant space. In other words, find the lowest positive integer that does not exist in the array. The array can contain duplicates and negative numbers as well.
For example, the input [3, 4, -1, 1] should give 2. The input [1, 2, 0] should give 3.
You can modify the input array in-place.
*/
#include <iostream>
using namespace std;
int calcMissing(int* input, int size)
{
int sum = 0;
int n = 1; //add one to account for missing value
for(int i = 0; i < size; i++)
{
if(input[i] > 0)
{
sum += input[i];
n++;
}
}
//If no numbers higher than 0, answer is 1
if(sum == 0)
return 1;
return (n*(n+1)/2) - sum; //Formula is expectedSum - actualSum
/* expectedSum = n*(n+1)/2, the formula for sum(1, n) */
}
int main()
{
cout << calcMissing(new int[4]{3, 4, -1, 1}, 4) << endl;
cout << calcMissing(new int[3]{1, 2, 0}, 3) << endl;
//No positive numbers
cout << calcMissing(new int[1]{0}, 1) << endl;
}

Audio Frequency Amplitudes

ThiccDaddyLOAF
0 likes • Aug 27, 2021
C++
//From https://create.arduino.cc/projecthub/abhilashpatel121/easyfft-fast-fourier-transform-fft-for-arduino-9d2677
#include <cmath>
#include <iostream>
const unsigned char sine_data[] = { //Quarter a sine wave
0,
4, 9, 13, 18, 22, 27, 31, 35, 40, 44,
49, 53, 57, 62, 66, 70, 75, 79, 83, 87,
91, 96, 100, 104, 108, 112, 116, 120, 124, 127,
131, 135, 139, 143, 146, 150, 153, 157, 160, 164,
167, 171, 174, 177, 180, 183, 186, 189, 192, 195, //Paste this at top of program
198, 201, 204, 206, 209, 211, 214, 216, 219, 221,
223, 225, 227, 229, 231, 233, 235, 236, 238, 240,
241, 243, 244, 245, 246, 247, 248, 249, 250, 251,
252, 253, 253, 254, 254, 254, 255, 255, 255, 255
};
float sine(int i){ //Inefficient sine
int j=i;
float out;
while(j < 0) j = j + 360;
while(j > 360) j = j - 360;
if(j > -1 && j < 91) out = sine_data[j];
else if(j > 90 && j < 181) out = sine_data[180 - j];
else if(j > 180 && j < 271) out = -sine_data[j - 180];
else if(j > 270 && j < 361) out = -sine_data[360 - j];
return (out / 255);
}
float cosine(int i){ //Inefficient cosine
int j = i;
float out;
while(j < 0) j = j + 360;
while(j > 360) j = j - 360;
if(j > -1 && j < 91) out = sine_data[90 - j];
else if(j > 90 && j < 181) out = -sine_data[j - 90];
else if(j > 180 && j < 271) out = -sine_data[270 - j];
else if(j > 270 && j < 361) out = sine_data[j - 270];
return (out / 255);
}
//Example data:
//-----------------------------FFT Function----------------------------------------------//
float* FFT(int in[],unsigned int N,float Frequency){ //Result is highest frequencies in order of loudness. Needs to be deleted.
/*
Code to perform FFT on arduino,
setup:
paste sine_data [91] at top of program [global variable], paste FFT function at end of program
Term:
1. in[] : Data array,
2. N : Number of sample (recommended sample size 2,4,8,16,32,64,128...)
3. Frequency: sampling frequency required as input (Hz)
If sample size is not in power of 2 it will be clipped to lower side of number.
i.e, for 150 number of samples, code will consider first 128 sample, remaining sample will be omitted.
For Arduino nano, FFT of more than 128 sample not possible due to mamory limitation (64 recomended)
For higher Number of sample may arise Mamory related issue,
Code by ABHILASH
Documentation:https://www.instructables.com/member/abhilash_patel/instructables/
2/3/2021: change data type of N from float to int for >=256 samples
*/
unsigned int sampleRates[13]={1,2,4,8,16,32,64,128,256,512,1024,2048};
int a = N;
int o;
for(int i=0;i<12;i++){ //Snapping N to a sample rate in sampleRates
if(sampleRates[i]<=a){
o = i;
}
}
int in_ps[sampleRates[o]] = {}; //input for sequencing
float out_r[sampleRates[o]] = {}; //real part of transform
float out_im[sampleRates[o]] = {}; //imaginory part of transform
int x = 0;
int c1;
int f;
for(int b=0;b<o;b++){ // bit reversal
c1 = sampleRates[b];
f = sampleRates[o] / (c1 + c1);
for(int j = 0;j < c1;j++){
x = x + 1;
in_ps[x]=in_ps[j]+f;
}
}
for(int i=0;i<sampleRates[o];i++){ // update input array as per bit reverse order
if(in_ps[i]<a){
out_r[i]=in[in_ps[i]];
}
if(in_ps[i]>a){
out_r[i]=in[in_ps[i]-a];
}
}
int i10,i11,n1;
float e,c,s,tr,ti;
for(int i=0;i<o;i++){ //fft
i10 = sampleRates[i]; // overall values of sine/cosine :
i11 = sampleRates[o] / sampleRates[i+1]; // loop with similar sine cosine:
e = 360 / sampleRates[i+1];
e = 0 - e;
n1 = 0;
for(int j=0;j<i10;j++){
c=cosine(e*j);
s=sine(e*j);
n1=j;
for(int k=0;k<i11;k++){
tr = c*out_r[i10 + n1]-s*out_im[i10 + n1];
ti = s*out_r[i10 + n1]+c*out_im[i10 + n1];
out_r[n1 + i10] = out_r[n1]-tr;
out_r[n1] = out_r[n1]+tr;
out_im[n1 + i10] = out_im[n1]-ti;
out_im[n1] = out_im[n1]+ti;
n1 = n1+i10+i10;
}
}
}
/*
for(int i=0;i<sampleRates[o];i++)
{
std::cout << (out_r[i]);
std::cout << ("\t"); // un comment to print RAW o/p
std::cout << (out_im[i]); std::cout << ("i");
std::cout << std::endl;
}
*/
//---> here onward out_r contains amplitude and our_in conntains frequency (Hz)
for(int i=0;i<sampleRates[o-1];i++){ // getting amplitude from compex number
out_r[i] = sqrt(out_r[i]*out_r[i]+out_im[i]*out_im[i]); // to increase the speed delete sqrt
out_im[i] = i * Frequency / N;
std::cout << (out_im[i]); std::cout << ("Hz");
std::cout << ("\t"); // un comment to print freuency bin
std::cout << (out_r[i]);
std::cout << std::endl;
}
x = 0; // peak detection
for(int i=1;i<sampleRates[o-1]-1;i++){
if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]){
in_ps[x] = i; //in_ps array used for storage of peak number
x = x + 1;
}
}
s = 0;
c = 0;
for(int i=0;i<x;i++){ // re arraange as per magnitude
for(int j=c;j<x;j++){
if(out_r[in_ps[i]]<out_r[in_ps[j]]){
s=in_ps[i];
in_ps[i]=in_ps[j];
in_ps[j]=s;
}
}
c=c+1;
}
float* f_peaks = new float[sampleRates[o]];
for(int i=0;i<5;i++){ // updating f_peak array (global variable)with descending order
f_peaks[i]=out_im[in_ps[i]];
}
return f_peaks;
}
//------------------------------------------------------------------------------------//
//main.cpp
int data[64]={
14, 30, 35, 34, 34, 40, 46, 45, 30, 4, -26, -48, -55, -49, -37,
-28, -24, -22, -13, 6, 32, 55, 65, 57, 38, 17, 1, -6, -11, -19, -34,
-51, -61, -56, -35, -7, 18, 32, 35, 34, 35, 41, 46, 43, 26, -2, -31, -50,
-55, -47, -35, -27, -24, -21, -10, 11, 37, 58, 64, 55, 34, 13, -1, -7
};
int main(){
const unsigned int SAMPLE_RATE = 48*1000; //48khz
auto result = FFT(data,64,SAMPLE_RATE);
std::cout << result[0] << " " << result[1] << " " << result[2] << " " << result[3] << std::endl;
delete[] result;
return 0;
}

Big O(n^2) Ascending Sort

AustinLeath
0 likes • Nov 18, 2022
C++
#include <iostream>
using namespace std;
int main() {
int dataEntry;
int arr[5];
for(int i = 0; i < 5; i++) {
cout << "Enter a number that you want to put into the array: ";
cin >> dataEntry;
arr[i] = dataEntry;
}
cout << endl;
for(int i = 0; i < 5; i++) {
cout << "Outputting array info at position " << i + 1 << ": " << arr[i] << endl;
}
for(int i=0;i<5;i++)
{
for(int j=i+1;j<5;j++)
{
if(arr[i]>arr[j])
{
int temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
}
}
cout << endl;
for(int i = 0; i < 5; i++) {
cout << "Outputting sorted array info at position " << i + 1 << ": " << arr[i] << endl;
}
return 0;
}

Two Letter Combinations

AustinLeath
0 likes • Nov 18, 2022
C++
#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
using namespace std;
//This program makes a new text file that contains all combinations of two letters.
// aa, ab, ..., zy, zz
int main(){
string filename = "two_letters.txt";
ofstream outFile;
outFile.open(filename.c_str());
if(!outFile.is_open()){
cout << "Something's wrong. Closing..." << endl;
return 0;
}
for(char first = 'a'; first <= 'z'; first++){
for(char second = 'a'; second <= 'z'; second++){
outFile << first << second << " ";
}
outFile << endl;
}
return 0;
}

Get Coefficient

AustinLeath
0 likes • Nov 18, 2022
C++
#include <iostream>
using namespace std;
/* Function: get_coeff
Parameters: double& coeff, int pos passed from bb_4ac
Return: type is void so no return, but does ask for user to input data that establishes what a b and c are.
*/
void get_coeff(double& coeff, int pos) {
char position;
if(pos == 1) {
position = 'a';
} else if(pos == 2) { //a simple system to determine what coefficient the program is asking for.
position = 'b';
} else {
position = 'c';
}
cout << "Enter the co-efficient" << position << ":"; //prompt to input coeff
cin >> coeff; //input coeff
}
/* Function: bb_4ac
Parameters: no parameters passed from main, but 3 params established in function, double a, b, c.
Return: b * b - 4 * a * c
*/
double bb_4ac() {
double a, b, c; //coefficients of a quadratic equation
get_coeff(a, 1); // call function 1st time
get_coeff(b, 2); // call function 2nd time
get_coeff(c, 3); // call function 3rd time
return b * b - 4 * a * c; //return b * b - 4 * a * c
}
int main() {
cout << "Function to calculate the discriminant of the equation. . . " << endl;
double determinate = bb_4ac(); //assign double determinate to bb_4ac function
cout << "The discriminant for given values is: " << determinate << endl; //output the determinate!
}