After taking the input for variable k,its value is automatically changing to 5.
#include<iostream>
using namespace std;
int search(int arr[], int target, int size) {
int l = 0; int mid;
while(l <= size) {
mid = l + (size-l) / 2;
if(arr[mid] == target)
return 1;
if(arr[mid] > target)
size = mid - 1;
if(arr[mid] < target)
l = mid + 1;
}
return 0;
}
int sort(int arr[], int size) {
int temp; bool swap = false;
for(int i = 0; i < size; i++) {
bool swap = false;
for(int j = 0; j < size - i; j++) {
if(arr[j] > arr[j + 1]) {
temp = arr[j + 1];
arr[j + 1] = arr[j];
arr[j] = temp;
swap = true;
}
}
if(swap == false)
break;
}
return 0;
}
int main() {
int n, k;
int count;
int j;
int arr[n];
cin >> n;
cin >> k;
int value;
for(int i = 0; i < n; i++)
cin >> arr[i];
sort(arr, n - 1);
for(int i = 0; i < n; i++) {
value=arr[i] + k;
j = search(arr, value, n - 1);
if(j == 1)
count++;
}
cout << count;
}
I printed the value of k just after the input and it shows the correct value. but inside the main function when i am using it to calculate the variable "value" its value is being taken as 5.Something is happening before the sort function is being called.
Related
I am trying to implement a hybrid of mergesort and insertion sort. When the subarray size reaches below a threshold, it should switch to insertion sort.
However I tried with a bunch of array of different length and different threshold amount, and most of the time there isn't any noticeable difference, other than just a 2-3 lesser comparisons. I was told that switching to insertion sort for smaller sized array would help greatly.
Am I doing it wrong?
#include <iostream>
int comparisons = 0;
int swaps = 0;
void mergesort(int x[], int l, int r);
void insertionSort(int x[],int start, int end);
int main() {
int x[] = {9,5,1,4,3,10,29,69,5,9,11,19,21,69,0,2,3,4,5,11,111,96,25,32,21,2,12,3,52,55,23,32,15,15,14,13,9,5,1,4,3,10,29,69,5,9,11,19,21,69,0,2,3,4,5,11,111,96,25,32,21,2,12,3,52,55,23,32,15,15,14,13,};
// insertionSort(x,10);
int sizeX= sizeof(x)/sizeof(x[0]) ;
mergesort(x, 0, sizeX-1);
for(int i =0;i<sizeX;i++){
std::cout << x[i] << " ";
}
// std::cout << "\nSWAPS: " << swaps;
std::cout << "\nCOMPARISONS: " << comparisons;
}
void insertionSort(int arr[], int start,int end)
{
int i, key, j;
for (i = start +1 ; i < end; i++)
{
key = arr[i];
j = i - 1;
/* Move elements of arr[0..i-1], that are
greater than key, to one position ahead
of their current position */
while (j >= 0 && arr[j] > key)
{
comparisons++;
arr[j + 1] = arr[j];
j = j - 1;
}
arr[j + 1] = key;
}
}
void insertionSort2(int x[],int start, int end){
for(int i =start; i < end;i++){
for (int j= i; j!= 0;j--){
comparisons++;
if(x[j] < x[j-1]){
int temp = x[j-1];
x[j-1] = x[j];
x[j] = temp;
swaps++;
}
else{
break;
}
}
}
}
void mergesort(int x[], int l, int r) {
if (l >= r)
return;
int mid = (l + r) / 2;
if(r - l < 3){
insertionSort(x, l,r+1);
}else{
mergesort(x, l, mid);
mergesort(x, mid + 1, r);
int i = l;
int j = mid + 1;
int k = 0;
int tmp[r - l + 1];
while (i <= mid && j <= r) {
comparisons++;
if (x[i] >= x[j]) {
tmp[k] = x[j];
j++;
} else {
tmp[k] = x[i];
i++;
}
swaps++;
k++;
}
while (i <= mid) {
tmp[k] = x[i];
i++;
k++;
}
while (j <= r) {
tmp[k] = x[j];
j++;
k++;
}
for (i = 0; i < k; i++) x[l + i] = tmp[i];
}
}
I've read many posts but I can't figure out where is my error so I go with it.
My program throws the segfault at the cout<<endl. When I erase it, the program doesn't even print anything. It just prints the segfault. Aparently the program never reach to sort the vector.
#include <iostream>
#include <vector>
using namesapce std
void inserctionSort(std::vector<double> &v, int i, int j)
{
double temp;
for(i; i < v.size(); i++)
{
temp = v[i];
j = i - 1;
while((v[j] > temp) && (j >= 0))
{
v[j+1] = v[j];
j--;
}
v[j+1] = temp;
}
}
void merge_(std::vector<double> &v, int i, int k, int j)
{
std::vector<double> w(v.size());
int n = j - i + 1;
int p = i;
int q = k + 1;
for(int l = 0; l < n; l++)
{
if(p <= k && (q > j || v[p] <= v[q]))
{
w[l] = v[p];
p++;
}else
{
w[l] = v[q];
q++;
}
}
for(int l = 0; l < n; l++)
v[i - 1 + l] = w[l];
}
void mergeSort(std::vector<double> &v, int i, int j)
{
int n = j - i + 1, n0 = 3;
int k;
if(n <= n0)
{
inserctionSort(v,i,j);
}else
{
k = i - 1 + n / 2;
mergeSort(v, i, k);
mergeSort(v, k + 1, j);
merge_(v, i, k, j);
}
}
int main()
{
vector<double> v1 = {3.2,4.1,55.42,2.24,5.424,667.32,35.54};
cout<<"Vector desordenado: ";
for(int i = 0; i < v1.size(); i++)
cout<<v1[i]<<", ";
cout<<"hola";
cout<<endl;
cout<<"hola";
mergeSort(v1, 0, v1.size()-1); //--> Core generado
//quickSort(v1, 0, v1.size()-1);
cout<<"Vector ordenado: ";
for(int i = 0; i < v1.size(); i++)
cout<<v1[i]<<", ";
return 0;
}
You have problems in your code with vector indices assuming value -1 inside a couple of loops.
I have corrected these mistakes below, a working version of your code:
#include <iostream>
#include <vector>
using namespace std;
void inserctionSort(vector<double> &v, int i, int j)
{
int v_size = v.size();
double temp;
for (; i < v_size; i++) {
temp = v[i];
j = i - 1;
while ( (j >= 0) && (v[j] > temp) ) { // swapped conditions, as when j=-1, v[j]>temp is undefined
v[j+1] = v[j];
j--;
}
v[j+1] = temp;
}
}
void merge_(vector<double> &v, int i, int k, int j)
{
vector<double> w( v.size() );
int n = j - i + 1;
int p = i;
int q = k + 1;
for (int l = 0; l < n; l++) {
if ( p <= k && (q > j || v[p] <= v[q]) ) {
w[l] = v[p];
p++;
} else {
w[l] = v[q];
q++;
}
}
for(int l = 0; l < n; l++)
v[i + l] = w[l]; // deleted -1 from v[i - 1 + l], as it leads to v[-1] for i,l = 0
}
void mergeSort(vector<double> &v, int i, int j)
{
int n = j - i + 1, n0 = 3; // n = v.size()
int k;
if (n <= n0) {
inserctionSort(v,i,j);
} else {
k = i - 1 + n / 2;
mergeSort(v, i, k);
mergeSort(v, k + 1, j);
merge_(v, i, k, j);
}
}
int main()
{
vector<double> v1 = {3.2,4.1,55.42,2.24,5.424,667.32,35.54};
cout<<"Vector desordenado: ";
for (unsigned i = 0; i < v1.size(); i++)
cout<<v1[i]<<", ";
cout << "hola";
cout << endl;
cout << "hola";
mergeSort(v1, 0, v1.size()-1); //--> Core generado
//quickSort(v1, 0, v1.size()-1);
cout<<"Vector ordenado: ";
for (unsigned i = 0; i < v1.size(); i++)
cout << v1[i] << ", ";
return 0;
}
In my code , lb refers to lower bound and ub refers to upper bound.I'm using the mergeSort function to recursively split the array into smaller pieces and the merge function to merge in their sorted order.
#include <iostream>
using namespace std;
void merge(int input[], int lb, int ub, int size)
{
int i = lb;
int k = 0;
int mid = (lb + ub) / 2;
int j = mid + 1;
int *arr = new int[size];
while (i <= mid && j <= ub)
{
if (input[i] <= input[j])
arr[k++] = input[i++];
else
arr[k++] = input[i++];
}
while (i <= mid)
arr[k++] = input[i++];
while (j <= ub)
arr[k++] = input[j++];
for (k = 0; k < size; k++)
input[k] = arr[k];
}
void mergeSort(int input[], int size)
{
int lb = 0;
int ub = size - 1;
int mid;
if (size == 0)
{
return;
}
else if (lb < ub)
{
mid = (lb + ub) / 2;
mergeSort(input, mid - lb + 1);
mergeSort(input + mid + 1, ub - mid);
merge(input, lb, ub, size);
}
else
{
return;
}
}
int main()
{
int input[1000], length;
cin >> length;
for (int i = 0; i < length; i++)
cin >> input[i];
mergeSort(input, length);
for (int i = 0; i < length; i++)
{
cout << input[i] << " ";
}
}
You have used i istead of j in the first while loop in merge function. The correct code is the following
while (i <= mid && j <= ub) {
if (input[i] <= input[j])
arr[k++] = input[i++];
else
arr[k++] = input[j++];
}
I need to be able to track the number of exchanges and comparisons in this selection sort algorithm. The algorithm sorts the array just fine. I need to modify it in order to have tracked the number of exchanges.
void insertion_sort(int * theArray, int size)
{
int tmp;
for (int i = 1; i < size; i++)
{
for (int j = i; j > 0 && theArray[j - 1] > theArray[j]; j--)
{
tmp = theArray[j];
theArray[j] = theArray[j - 1];
theArray[j - 1] = tmp;
}
}
}
Here are the two helper functions
bool inOrder(int i, int j) {
numComparisons++;
return i <= j;
}
void swapElement(int & i, int & j) {
int t = i;
i = j;
j = t;
numSwaps++;
}
Something like that ?
void insertion_sort(int * theArray, int size)
{
int tmp;
int count = 0;
for (int i = 1; i < size; i++)
{
for (int j = i; j > 0 && theArray[j - 1] > theArray[j]; j--)
{
tmp = theArray[j];
theArray[j] = theArray[j - 1];
theArray[j - 1] = tmp;
count++; // increment on each loop/exchanges
}
}
}
I have written code for matrix chain multiplication in dynamic programming in c++.
there is an error in the recursive call for printing the correct parenthesization of the matrices. I am taking input from text file and giving output on a text file. please help..
#include <iostream>
#include <fstream>
#include <limits.h>
using namespace std;
int * MatrixChainOrder(int p[], int n)
{
static int m[100][100];
static int s[100][100];
int j, q;
int min = INT_MAX;
for (int i = 1; i <= n; i++)
m[i][i] = 0;
for (int L = 2; L <= n; L++) {
for (int i = 1; i <= n - L + 1; i++) {
j = i + L - 1;
m[i][j] = min;
for (int k = i; k <= j - 1; k++) {
q = m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j];
if (q < m[i][j]) {
m[i][j] = q;
s[i][j] = k;
}
}
}
}
return (*s);
}
void Print(int *s, int i, int j)
{
ofstream outfile("output.text");
if (i == j)
{
outfile << "a1";
}
else
outfile << "(";
{
Print(*s, i, s[i][j]);
Print(*s, s[i][j] + 1, j);
outfile << ")";
}
outfile.close();
}
int main()
{
int arr[100];
int num, i = 0;
ifstream infile("input.text");
while (infile)
{
infile >> num;
arr[i] = num;
i++;
}
i = i - 1;
infile.close();
Print(MatrixChainOrder(arr, i - 1), 0, i - 1);
return 0;
}
In C++ it is better to use std::vector for arrays. Aside from that, you can't mix pointers and arrays like that because the compiler loses track of array size.
For example this doesn't work:
int x[10][20];
void foo(int *ptr)
{
//the numbers 10 and 20 have not been passed through
}
But you can change it to
int x[10][20];
void foo(int arr[10][20])
{
//the numbers 10 and 20 are available
}
MatrixChainOrder is supposed to return a number, according to this link
int MatrixChainOrder(int s[100][100], int p[], int n)
{
int m[100][100];
for (int i = 0; i < 100; i++) m[i][i] = 0;
for (int i = 0; i < 100; i++) s[i][i] = 0;
int q = 0;
for (int L = 2; L <= n; L++) {
for (int i = 1; i <= n - L + 1; i++) {
int j = i + L - 1;
m[i][j] = INT_MAX;
for (int k = i; k <= j - 1; k++) {
q = m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j];
if (q < m[i][j]) {
m[i][j] = q;
s[i][j] = k;
}
}
}
}
return q;
}
int main()
{
int arr[] = { 40, 20, 30, 10, 30 };
int array_size = sizeof(arr) / sizeof(int);
int n = array_size - 1;
int s[100][100];
int minimum = MatrixChainOrder(s, arr, n);
printf("{ 40, 20, 30, 10, 30 } should result in 26000 : %d\n", minimum);
return 0;
}
Likewise you can change your Print function
void Print(int s[100][100], int i, int j)
{
if (i < 0 || i >= 100 || j < 0 || j >= 100)
{
cout << "array bound error\n";
}
//safely access s[i][j] ...
}