I'm trying to implement insertion sort. My logic may be wrong because I was unable to complete my code due to some error.
I want help with values changing absurdly while executing. Also, there is a similar repeating element question but it is in python and it went over my head. so, please don't mark it duplicate.
As you can see I have initialized a temporary variable index, why you ask? because the value of N is changing during run time.
secondly, Value is getting repeated when sorting is taking place.
I'm using codeblocks 17.2.
#include<iostream>
#include<utility>
#include<algorithm>
using namespace std;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int arr[100];
int N,index;
cin>>N;
for(int i=0;i<N;i++)
{
cin>>arr[i];
}
index=N; // using temperory variable
for(int l=0;l<index;l++)
{
for(int j=l+1;j>=0;j--)
{
if(l==index-1 || j==0) //Working fine now
break;
if(arr[j]<arr[j-1])
{
swap(arr[j],arr[j-1]);
}
}
cout<<N<<endl; //value of n is changing but why
for(int k=0;k<index;k++)
{
cout<<arr[k]<<" "; //value of array is also coming wrong
}
cout<<"\n";
}
return 0;
}
N=7
and elements of the array to be
7 8 5 2 4 6 3
output is
7 //these are the values of N which is changing
7 8 5 2 4 6 3
5
7 7 8 2 4 6 3
2
5 7 7 8 4 6 3
2
4 5 7 7 8 6 3
2
4 5 6 7 7 8 3
2
3 4 5 6 7 7 8
0
2 3 4 5 6 7 7
check for boundary condition and when non-existing array index is accessed it will give undefined behavior. In this case, it appears that N was stored right before arr and it changed when you modified arr[-1].
Related
I was trying to solve a problem where I had to sort so I used the standard library std::sort function but I get a wrong output in the 2nd test case:
#include <bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
{
int n,i;
cin>>n;
int arr[n-1];
for(i=1;i<=n-1;i++)
cin>>arr[i];
int size=sizeof(arr)/sizeof(arr[1]);
sort(arr,arr+size);
for(i=1;i<=n-1;i++)
cout<<arr[i]<<" ";
cout<<endl;
}
return 0;
}
I/P:
2
5
1 2 5 4
10
1 2 3 4 5 6 7 8 10
Expected O/P:
1 2 4 5
1 2 3 4 5 6 7 8 10
Actual O/P:
1 2 4 5
2 3 4 5 6 7 8 2013562 10
First of all, int arr[n-1]; is a variable length array. That's not actually part of C++, even though some compilers will tolerate it nevertheless. In most cases you can just use std::vector<int>(n-1); instead.
But look at this loop:
for(i=1;i<=n-1;i++)
cin>>arr[i];
You're starting at 1 and got all the way up to n-1, however your array goes from arr[0] to arr[n-2]. So you got undefined behavior because you're writing one past the size of the array, and you also don't write to the first position (leading to more undefined behavior when you try to sort with this uninitialized value still present).
Instead, the loop should be for(i=0;i<n-1;i++) The same applies to where you're printing it. You can then sort the vector this way:
sort(arr.begin(), arr.end());
Also note that by doing n-1 you're always reading in and handling one less value that the user inputs, I'm not sure if that's your intention. If you want that, you could also just decrease n by one after reading it in instead of writing n-1 in multiple places.
OK I am trying to make Prima algorithm so i need my edges array sorted, I tried to use quicksort here but it didn't work as I planned.
#include <iostream>
using namespace std;
void Sort (int arr[100][4], int m, int l) {
int i,j,x,v;
i=m;
j=l;
x=(i+j)/2;
do
{
while (((arr[i][3]<arr[x][3]))and(i<=l)) i++;
while (((arr[j][3]>arr[x][3]))and(j>=m)) j--;
if (i<=j)
{
v=arr[i][1];
arr[i][1]=arr[j][1];
arr[j][1]=v;
v=arr[i][2];
arr[i][2]=arr[j][2];
arr[j][2]=v;
v=arr[i][3];
arr[i][3]=arr[j][3];
arr[j][3]=v;
i++;
j--;
}
}
while (i<=j);
if (i<l) Sort(arr,i,l);
if (m<j) Sort(arr,m,j);
}
int main () {
int i,x,y,z,n,m;
int a[100][4];
fill(&a[0][0],&a[0][0]+400,0);
cout<<"Enter number of nodes and edges\n";
cin>>n>>m;
cout<<"Enter edges and their weights\n";
for (i=0;i<m;i++) {
cin>>x>>y>>z;
a[i][1]=min(x,y);
a[i][2]=max(x,y);
a[i][3]=z;
}
Sort (a,0,m-1);
for (i=0;i<m;i++) {
cout<<i+1<<") "<<a[i][1]<<' '<<a[i][2]<<' '<<a[i][3]<<endl;
}
return 0;
}
what I put is
5 10
1 2 4
1 3 7
4 1 5
5 1 8
2 3 3
2 4 6
2 5 6
3 4 8
3 5 2
4 5 4
what I get is
1) 3 5 2
2) 2 3 3
3) 1 4 5
4) 1 2 4
5) 4 5 4
6) 2 5 6
7) 2 4 6
8) 1 3 7
9) 1 5 8
10) 3 4 8
I don't understand why 5 is going ahead of 4's. Hope you could help.
You choose the pivot element in the middle of the (sub)array, which is fine, but you leave it in that position when you run the partitioning loop, and rely on it to stay there, which is not ok. With your approach, the pivot is likely to be swapped to a different position during the ordinary course of partitioning, after which the remainder of the partitioning will be based on the key swapped into the pivot's original position, which is likely to be different.
The usual approach is to start by swapping the pivot element to one end of the array or the other, partition the rest of the array, and then afterward swap the pivot into its correct position, as discovered via the partitioning process.
Change the code to use the pivot value instead of the pivot index, and some fixes to make it more like conventional Hoare partition scheme:
i=m-1;
j=l+1;
x=arr[(i+j)/2][3];
while(1)
{
while (arr[++i][3] < x);
while (arr[--j][3] > x);
if(i >= j)
return j;
// ...
I am newbie on codechef and i was trying to solve the following question however my code runs fine on my machine, i also tested it with some cases.
Question is as follows :-
In Byteland it is always the military officer's main worry to order his soldiers on parade correctly. Luckily, ordering soldiers is not really such a problem. If a platoon consists of n men, all of them have different rank (from 1 - lowest to n - highest) and on parade they should be lined up from left to right in increasing order of rank.
Sounds simple, doesn't it? Well, Sgt Johnny thought the same, until one day he was faced with a new command. He soon discovered that his elite commandos preferred to do the fighting, and leave the thinking to their superiors. So, when at the first rollcall the soldiers lined up in fairly random order it was not because of their lack of discipline, but simply because they couldn't work out how to form a line in correct order of ranks. Sgt Johnny was not at all amused, particularly as he soon found that none of the soldiers even remembered his own rank. Over the years of service every soldier had only learned which of the other soldiers were his superiors. But Sgt Johnny was not a man to give up easily when faced with a true military challenge. After a moment's thought a solution of brilliant simplicity struck him and he issued the following order: "men, starting from the left, one by one, do: (step forward; go left until there is no superior to the left of you; get back in line).". This did indeed get the men sorted in a few minutes. The problem was solved... for the time being.
The next day, the soldiers came in exactly the same order as the day before, and had to be rearranged using the same method. History repeated. After some weeks, Sgt Johnny managed to force each of his soldiers to remember how many men he passed when going left, and thus make the sorting process even faster.
If you know how many positions each man has to walk to the left, can you try to find out what order of ranks the soldiers initially line up in?
Input
The first line of input contains an integer t<=50, the number of test cases. It is followed by t test cases, each consisting of 2 lines. The first line contains a single integer n (1<=n<=200000). The second line contains n space separated integers wi, denoting how far the i-th soldier in line must walk to the left when applying Sgt Johnny's algorithm.
Output
For each test case, output a single line consisting of n space separated integers - the ranks of the soldiers, given from left to right in their initial arrangement.
Example
Input:
2
3
0 1 0
5
0 1 2 0 1
Output:
2 1 3
3 2 1 5 4
Warning: large Input/Output data, be careful with certain languages
#include <iostream>
#include <string.h>
using namespace std;
int main ()
{
int t,n;
cin >> t;
while(t>0){
cin >> n;
int array[n+1];
int stepsmoved,i;
for(i = 1; i <= n; i++){
array[i] = i;
}
for(i = 1; i <=n; i++){
cin >> stepsmoved;
if(stepsmoved == 0){}
else{
int x;
x = array[i];
for (int j = i; j> i- stepsmoved; j--){
array[j] = array[j-1];
}
array[i-stepsmoved] = x;
}
}
for(i = 1; i <= n; i++){
cout<<array[i]<<" ";
}
cout<<endl;
t--;
}
return 0;
}
So is there something logically or syntactically wrong?
The order of 'unwinding' the sorting is relevant.
Here is the code that demonstrates the statement above (the ranks are 1-based, the 1 - is highest, 10 - is lowest, array indices are 0-based):
#include <stdio.h>
void dump(int *a) {
int i;
for (i = 0; i < 10; i++)
printf("%d ", a[i]);
printf("\n");
}
int main() {
int array[10] = {0}, steps[10] = {0};
int i,j;
srand(0);
// Assign ranks in random order
for (i = 0; i < 10;) {
j = rand() % 10;
if (!array[j])
array[j] = ++i;
}
dump(array);
// Sort according to the Sgt Johnny's initial idea
for (i = 1; i < 10; i++) {
for (j = 0; array[j] < array[i]; j++);
if (j < i) {
int k, temp = array[i];
for (k = i; k > j; k--) {
array[k] = array[k-1];
steps[temp-1]++;
}
array[j] = temp;
dump(array);
}
}
printf("Steps:\n");
dump(steps);
printf("\n");
// reconstruct the origina order
#if 1
for (i = 10-1; i >= 0; i--)
#else
for (i = 0; i < 10; i++)
#endif
{
int s = steps[array[i]-1];
for (j = i; s; s--, j++) {
int temp = array[j];
array[j] = array[j+1];
array[j+1] = temp;
}
dump(array);
}
}
If the reconstruction is done in reverse order, then we get a sequence that matches original:
8 7 5 1 10 4 2 3 9 6
7 8 5 1 10 4 2 3 9 6
5 7 8 1 10 4 2 3 9 6
1 5 7 8 10 4 2 3 9 6
1 4 5 7 8 10 2 3 9 6
1 2 4 5 7 8 10 3 9 6
1 2 3 4 5 7 8 10 9 6
1 2 3 4 5 7 8 9 10 6
1 2 3 4 5 6 7 8 9 10
Steps:
3 5 5 4 2 4 1 0 1 0
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 10 9
1 2 3 4 5 6 7 8 10 9
1 2 3 4 5 6 8 7 10 9
1 2 3 4 5 8 7 10 9 6
1 2 3 4 8 7 5 10 9 6
1 2 3 8 7 5 10 4 9 6
1 2 8 7 5 10 4 3 9 6
1 8 7 5 10 4 2 3 9 6
8 7 5 1 10 4 2 3 9 6
Otherwise, the reconstructed order does not match the original:
8 7 5 1 10 4 2 3 9 6
7 8 5 1 10 4 2 3 9 6
5 7 8 1 10 4 2 3 9 6
1 5 7 8 10 4 2 3 9 6
1 4 5 7 8 10 2 3 9 6
1 2 4 5 7 8 10 3 9 6
1 2 3 4 5 7 8 10 9 6
1 2 3 4 5 7 8 9 10 6
1 2 3 4 5 6 7 8 9 10
Steps:
3 5 5 4 2 4 1 0 1 0
2 3 4 1 5 6 7 8 9 10
2 4 1 5 6 7 3 8 9 10
2 4 5 6 7 1 3 8 9 10
2 4 5 7 1 3 8 6 9 10
2 4 5 7 3 8 6 1 9 10
2 4 5 7 3 8 6 1 9 10
2 4 5 7 3 8 1 9 10 0
2 4 5 7 3 8 1 10 9 0
2 4 5 7 3 8 1 10 0 9
2 4 5 7 3 8 1 10 0 6
I need to do a program and the input is a set of data with 6 lines and with 3 numbers separated by spaces, with a 'c' or with a 'f' in the last line:
input:
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
c
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
c
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
f
If the last letter after the 6 lines is a c, continue with other 6 lines and if it is a f, finish.
I intend with:
int main(){
char a;
int triangulo[6][3];
do{
for(int i=0; i<6; i++){
cin>>triangulo[i][0]>>triangulo[i][1]>>triangulo[i][2];
}
cin>>a;
}while(a != 'f');
system("pause");
}
But it now works, can you help me.
Because I do not how can I recieve 3 numbers in the same line, separated by spaces and receive very much data set.
And another question. For example, if the user write c 7 times, I need create an array for each data set??
input:
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
c
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
c
4 5 6
7 8 9
7 8 9
4 5 6
7 8 9
7 8 9
f
And if I have to sum each array and the sum is my output, I need to create an array for each data set??
output
126
126
126
Something like this should work for reading three digits.
cin>>triangulo[0] >> triangulo[1] >> triangulo[2];
However, if you are reading numbers (1, 2, 3, 18, 33, 418 or some such), you probably want to use int triangulo[3]; instead. And if you actually want to store 6 sets of three numbers, you will need a two-dimensional array:
int triangulo[6][3];
...
cin>>triangulo[i][0] >> triangulo[i][1] >> triangulo[i][2];
try this?
int main(){
char a;
int triangulo[3];
int sum=0;
do{
for(int i=0; i<6; i++){
cin>>triangulo[0] >> triangulo[1] >> triangulo[2];
sum=sum+triangulo[0]+triangulo[1]+triangulo[2];
}
cin>>a;
}while(a != 'f');
cout<<sum;
system("pause");
}
If you wish to store all the arrays, you can make the user to input a number(how many arrays will there be) before input the arrays and allocate the memory using new.
I've run into a really strange issue. I can reproduce on my win7 laptop as well as an ubuntu machine.
I have a C++ program like so:
#include <string>
#include <sstream>
#include <iostream>
using namespace std;
int main() {
for (int i = 0; i < 9; i++) {
string line;
getline(cin, line);
stringstream ss(line);
for (int j = 0; j < 9; j++) {
int p = 8;
ss >> p;
cout << p;
}
cout << endl;
}
return 0;
}
Now, if i compile it an run it with ./a.out < test.txt where text.txt contains:
1 2 3 4 5 6 7 8 9
2 2 3 4 5 6 7 8 9
3 2 3 4 5 6 7 8 9
4 2 3 4 5 6 7 8 9
5 2 3 4 5 6 7 8 9
6 2 3 4 5 6 7 8 9
7 2 3 4 5 6 7 8 9
8 2 3 4 5 6 7 8 9
9 2 3 4 5 6 7 8 9
It will output (without spaces):
8 8 8 8 8 8 8 8 8
2 2 3 4 5 6 7 8 9
3 2 3 4 5 6 7 8 9
4 2 3 4 5 6 7 8 9
5 2 3 4 5 6 7 8 9
6 2 3 4 5 6 7 8 9
7 2 3 4 5 6 7 8 9
8 2 3 4 5 6 7 8 9
9 2 3 4 5 6 7 8 9
Why is the first line wrong? I've tried reading the first line out of the loop as well.
Also, if I replace ss > p with cin > p I just get an output table full of 8's.
This is not making any sense!!
Okay you guys were right. Some weird stuff as the first character of my input file:
od -c test.txt
0000000 357 273 277 2 0 5 0 0 7 0
0000020 0 6 \n 4 0 0 9 6 0
0000040 0 2 0 \n 0 0 0 0 8
It's a problem with the data (since the code looks OK). Most probably you've saved your text file with UTF-8 encoding with BOM. An UTF-8 BOM is three bytes at the start of the file, and trying to interpret those as a decimal number specification would fail.
Second, third, fourth line etc. OK because you're creating new istringstream object for each line, so not retaining error mode from previous line.
So, fix: save the file without BOM -- assuming the BOM hypothesis is correct.
Cheers & hth.,
Your code seems fine to me, if I were you I'd double check the input file : are you sure there is no empty first line, or some non-numeric character on the beginning of line 1 ?
I suspect you wrote your own getline(), and the bug is there. InputStreams have a getline(char*, int), and I suspect your cramming string.begin() into the first param, and Some Other Number into the latter.
Don't do that.
All your program should be doing is copying the input to the output (given this code and that input). It's not doing that either, even on the lines that "work".
I am seeing a number of Not So Experienced Programmer 'signatures' here.
1) Overly short variable names (outside a for loop counter), "ss" and "p"
2) Magic error number (8), particularly one that doesn't stand out from the data.
3) "using"
1 and 3 both hint at a lack of typing speed, and therefore experience... despite your 1k+ reputation (which is based mostly on asking questions... the situation becomes clearer).
I'd rewrite it something like this:
int curDig;
curLine >> curDig;
if (curLine.good()) {
cout << curDig;
} else {
cout << "FAILED at line: " << lineIdx << " containing: " << line << std::endl;
}
Chances are, you're going to see "FAILED at line: 0 containing: " right out of the gate, due to what I think is a bug in your getline().