I am trying to implement a vector using my own class so I can not do the initialiser list part
# include <iostream>
# include <exception>
# include<initializer_list>
template <class T>
class vector {
public:
T* a;
T n;
int pos, c;
vector() { a = 0; n = 0; }
vector(T n) : n(n) { a = new T[n]; }
vector(std::initializer_list <vector> l) {
a = new T[int(sizeof(l))];
for (int f : l)
*(a + f) = l.begin() + f;
}
void push_back(T k) {
int i = k;
*(a + n) = k;
}
vector& operator= (vector&& th) {
this->a = th.a;
th.a = nullptr; return (*this);
}
vector& operator=(vector& k)
{
this->a = k.a;
return(*this);
}
int size() { return n; }
void pop_back() { *(a + n) = nullptr;
n--;
}
void resize(int c) {
delete a;
n = c;
a = new T[c];
}
T operator[](int pos) {
if (pos > sizeof(a))
std::cout << "out of range";
else return *(a + pos);
}
};
int main() {
vector<int> a(10);
vector<char>b{ 'w','b','f','g' };
getchar();
return 0;
}
I am just trying to use pointer offset notation to take the initializer list items into the dynamic array but I get errors VS 17 IDE
Severity Code Description Project File Line Suppression
Error C2440 '=': cannot convert from 'const _Elem *' to 'T'
Error C2440 'initializing': cannot convert from 'const _Elem' to 'int'
Hello Nimrod!
#include <iostream>
#include <exception>
#include <initializer_list>
// normally people don't place a space between '#' and 'include'
template <class T>
class vector {
public:
T* a;
int n;
// probably it is length the vector
// change T to int
int pos, c;
vector() {
a = nullptr;
// do not use '0' to instruct null pointer
n = 0;
}
vector(int n): n(n) { a = new T[n]; }
vector(std::initializer_list<T> l) {
a = new T[l.size()];
// redundant force cast from size_t to int
for (int i = 0; i < l.size(); i++) {
a[i] = l.begin()[i];
}
// for (int f : l) # it seems that you wrote JavaScript before?
// *(a + f) = l.begin() + f;
}
void push_back(T k) {
// assigns "T k" to "int i"? it's confusing
// int i = k;
// *(a + n) = k;
}
// probably still many problems
vector& operator=(vector&& th) {
this->a = th.a;
th.a = nullptr;
return (*this);
}
vector& operator=(vector& k) {
this->a = k.a;
return(*this);
}
int size() { return n; }
void pop_back() { *(a + n) = nullptr;
n--;
}
void resize(int c) {
delete a;
n = c;
a = new T[c];
}
T operator[](int pos) {
if (pos > sizeof(a))
std::cout << "out of range";
else return *(a + pos);
}
};
int main() {
vector<int> a(10);
vector<char>b{ 'w','b','f','g' };
getchar();
return 0;
}
You still need more practice. XP
In your context of code, template variable for initializer_list should be T rather than int.
Range for loop with initializer_list<T> will fetch the values
in the list. Therefore it should belong to T.
I've a Template Class array_T which is a general purpose array and a Template function linear search TEMPLATE.h and its declared as friend for the class arrayTemplate.h so it could be able to use the class's member function getArraySize() and the class's data member a which is a dynamic allocation array
arrayTemplate.h
#ifndef arrayTemplate
#define arrayTemplate
#include"linear search TEMPLATE.h"
#include<iostream>
using namespace std;
template <class T>
class array_T {
private:
T *a;
int arraySize;
public :
friend void linearSearch(array_T object);
array_T(int s) {
arraySize = s;
a = new T[arraySize];
for (int i= 0; i < arraySize; ++i) {
a[i] = 0;
}
}
~array_T() {
delete[]a;
}
void setArray() {
for (int i=0; i < arraySize; ++i) {
cout << "Enter the elements of the array " << endl;
cin >> a[i];
}
}
void getArray() {
for (int i=0; i < arraySize; ++i) {
cout << a[i] << endl;
}
}
int getArraySize() {
return arraySize;
}
};
#endif
linear search TEMPLATE.h
#include"arrayTemplate.h"
#include<iostream>
using namespace std;
template <class T>
//void linearSearch(T desiredData, int arraySize, T *elemnts) {
void linearSearch(array_T<T> object , T desiredData) {
int arraySize = object.getArraySize();
int loc = -1;
int i = 0;
for (i = 0; i < arraySize; ++i) {
if (object.a[i] == desiredData) {
loc = i;
break;
}
}
if (loc > 0) {
cout << "the Item is found at position " << i + 1 << endl;
}
else {
cout << "the item is not found ";
}
}
main.cpp
#include"arrayTemplate.h"
#include"linear search TEMPLATE.h"
#include<iostream>
using namespace std;
int main() {
array_T<int> myArray(7);
myArray.setArray();
linearSearch(myArray,50)
return 0 ;
}
these are the errors i got
linear search template.h(8): error C2065: 'array_T': undeclared
identifier
linear search template.h(8): error C2065: 'object': undeclared
identifier
linear search template.h(8): error C2275: 'T': illegal use of this
type as an expression
linear search template.h(6): note: see declaration of 'T'
linear search template.h(8): error C2146: syntax error: missing ')'
before identifier 'desiredData'
main.cpp(14): error C2660: 'linearSearch': function does not take 2
arguments
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
Given a horizontal section of wall , and N layers of paints applied from co-ordinates Xi to Yi , Output the distinct number of layers visible.
Here is the problem link http://www.spoj.com/problems/POSTERS/
Here is my solution http://ideone.com/gBJKnL
Approach :
I tried solving the problem by lazily updating child node values through a Segment Tree , the most recent value replaces the older one in their lazy updates. This way only the recent paint gets applied into the horizontal cross-section. although the code works fine on custom test cases , It takes a lot of memory and gets aborted by the Online Judge .
#include <iostream>
#include <set>
#include <vector>
#define MAX 10000000+100
typedef long long int ll;
using namespace std;
ll Tree[3*MAX],lazy[MAX*2];
void Update(ll s,ll start,ll end,ll left,ll right,ll value)
{
if(lazy[s]!=0)
{
Tree[s]=(lazy[s]*(end-start+1));
if(start!=end)lazy[2*s+1]=lazy[s],lazy[s*2+2]=lazy[s];
lazy[s]=0;
}
if(start>end||left>end||right<start)return;
if(start>=left&&end<=right)
{
Tree[s] = (value*(end-start+1));
if(start!=end)
{
lazy[2*s+1]=value;
lazy[2*s+2]=value;
}
return ;
}
ll mid=(start+end)/2;
Update(2*s+1,start,mid,left,right,value);
Update(2*s+2,mid+1,end,left,right,value);
Tree[s] = Tree[s*2+1]+Tree[2*s+2];
}
ll Read(ll s,ll start,ll end,ll left,ll right)
{
if(start>end||start>right||end<left)return 0;
if(lazy[s]!=0)
{
Tree[s]=(lazy[s]*(end-start+1));
if(start!=end)
{
lazy[2*s+1]=lazy[s];
lazy[2*s+2]=lazy[s];
}
lazy[s]=0;
}
if(start>=left&&end<=right)return Tree[s];
else return (Read(2*s+1,start,(start+end)/2,left,right)+Read(2*s+2,1+((start+end)/2),end,left,right));
}
int main() {
// your code goes here
ll t;
cin>>t;
while(t--)
{
ll n,z=1,li=-1;
cin>>n;
vector<pair<ll,ll> > b;
for(ll i=0;i<n;i++)
{
ll u,v;
li = max(li,v);
cin>>u>>v;
b.push_back(make_pair(u-1,v-1));
}
for(auto v: b)
Update(0,0,li+2,v.first,v.second,z++);
set<ll> a;
for(ll i=0;i<li+2;i++)cout<<Read(0,0,li+2,i,i)<<" ",a.insert(Read(0,0,li+2,i,i));
cout<<endl;
cout<<a.size()-1<<endl;
}
return 0;
}
Here is how you should be doing it:
#include <bits/stdc++.h>
#define mx 400005
using namespace std;
int tr[mx], lz[mx];
int t, n, l, r;
void update(int node, int s, int e, int l, int r, int val)
{
if(lz[node]!=0)
{
tr[node]=lz[node];
if(s!=e)
{
lz[node*2]=lz[node];
lz[node*2+1]=lz[node];
}
lz[node]=0;
}
if(s>e || r<s || l>e)
return;
if(s>=l && e<=r)
{
tr[node]=val;
if(s!=e)
{
lz[2*node]=val;
lz[2*node+1]=val;
}
return;
}
int m=s+(e-s)/2;
update(2*node,s,m,l,r,val);
update(2*node+1,m+1,e,l,r,val);
tr[node]=val;
//tr[node]=max(tr[2*node],tr[2*node+1]);
}
int query(int node, int s, int e, int l, int r)
{
if(r<s || e<l)
return 0;
if(lz[node]!=0)
{
tr[node]=lz[node];
if(s!=e)
{
lz[node*2]=lz[node];
lz[node*2+1]=lz[node];
}
lz[node]=0;
}
if(l<=s && r>=e)
return tr[node];
int m=s+(e-s)/2;
return query(2*node,s,m,l,r)+query(2*node+1,m+1,e,l,r);
}
int main()
{
//cout << "Hello world!" << endl;
cin>>t;
while(t--)
{
for(int i=0; i<mx; i++) tr[i]=0;
cin>>n;
int lr[n+1][2];
map<int,bool> mark;
vector<int> vec;
//int c=0;
for(int i=0; i<n; i++)
{
cin>>l>>r;
lr[i][0]=l;
lr[i][1]=r;
if(mark[l]==0)
{
vec.push_back(l);
mark[l]=1;
}
if(mark[r]==0)
{
vec.push_back(r);
mark[r]=1;
}
}
sort(vec.begin(), vec.end());
map<int,int> mp;
int c=1;
for(int i=0; i<vec.size(); i++)
mp[vec[i]]=c++;
for(int i=0; i<n; i++)
{
//cout<<mp[lr[i][0]]<<" "<<mp[lr[i][1]]<<"\n";
update(1,1,vec.size(),mp[lr[i][0]],mp[lr[i][1]],i+1);
}
set<int> ans;
for(int i=1; i<=vec.size(); i++)
{
//cout<<query(1,1,vec.size(),i,i)<<" ";
ans.insert(query(1,1,vec.size(),i,i));
}
int k = ans.size();
if(ans.find(0) != ans.end())
k--;
printf("%d\n",k);
}
return 0;
}
Im a new programmer in C++ and I want to creat a code that extract IP from text files
I tried to convert txt file to Vector(string) to be easy filtering but i cant get all formes like XXX.XXX.XXX.XXX
Given that the ip could be embedded in some text, we'll parse the string and fetch it.
#include <iostream>
#include <string>
#include <iterator>
#include <vector>
#include <sstream>
using namespace std;
string ip(string str)
{
//middle portion
auto firstDot = str.find_first_of('.');
auto lastDot = str.find_last_of('.');
int dotCount = 0;
for(auto i = firstDot; i <= lastDot; i++)
{
if(!isdigit(str.at(i)) && str.at(i) != '.') //e.g 127.ss.0y.1
return string("");
if(str.at(i) == '.')
dotCount++;
}
if(dotCount != 3) //eg. 127.0.1 (not sure if this is wrong though)
return string("");
string result = str.substr(firstDot,lastDot-firstDot + 1);
//left portion
size_t x = 0; //number consegative digits from the first dot
for(auto i = firstDot-1; i >= 0; i--)
{
if(!isdigit(str.at(i)))
break;
else if(x == 3) //take first 3
break;
x++;
}
if(x == 0)
return string("");
result.insert(0,str.substr(firstDot-x,x));
//right portion
size_t y = 0;
for(auto i = lastDot + 1; i < str.length(); i++)
{
if(isdigit(str.at(i)))
{
if(y == 3)
break;
result.push_back(str.at(i));
y++;
}
else
break;
}
if(y == 0)
result.push_back('0');
return result;
}
int main()
{
string test = "1111127.0.0.11111 xx23.45.12.# xxxx.34.0.13 124.sd.2.1 sd.45.56.1";
string x,y;
vector<string> ips;
stringstream stream;
stream<<test;
while(stream>>x)
if(!(y = ip(x)).empty())
ips.push_back(y);
for(auto z : ips)
cout<<z<<"\t";
cout<<endl;
system("pause");
return 0;
}
#include<iostream>
#include<fstream>
using namespace std;
int main() {
ifstream myReadFile;
myReadFile.open("text.txt");
char output[100];
if (myReadFile.is_open()) {
while (!myReadFile.eof()) {
myReadFile >> output;
cout<<output;
}
}
myReadFile.close();
return 0;
}
Use this if the text file only includes IP's on each line.
Or depending on what c++ you're using:
std::ifstream file("Read.txt");
std::string str;
std::string file_contents;
while (std::getline(file, str))
{
file_contents += str;
file_contents.push_back('\n');
}
I'm new to C++11. I did the following simple example for you. It's based on the regex library. Hope it works for you!
#include <iostream>
#include <string>
#include <regex>
int main ()
{
std::string s ("There's no place like 127.0.0.1\n");
std::smatch m;
std::regex e ("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}");
while (std::regex_search (s,m,e)) {
for (auto x:m) std::cout << x << " ";
std::cout << std::endl;
s = m.suffix().str();
}
return 0;
}
I'm trying to figure out how much the execution time of boost::variant differ from a polymorphism approach. In my first test I got very different results on gcc 4.9.1 and clang+llvm 3.5.
You can find the code below. Here are my results:
clang+llvm
polymorphism: 2.16401
boost::variant: 3.83487
gcc:
polymorphism: 2.46161
boost::variant: 1.33326
I compiled both with -O3.
Is someone able to explain that?
code
#include <iostream>
#include <vector>
#include <algorithm>
#include <boost/variant.hpp>
#include <boost/variant/apply_visitor.hpp>
#include <ctime>
struct value_type {
value_type() {}
virtual ~value_type() {}
virtual void inc() = 0;
};
struct int_type : value_type {
int_type() : value_type() {}
virtual ~int_type() {}
void inc() { value += 1; }
private:
int value = 0;
};
struct float_type : value_type {
float_type() : value_type() {}
virtual ~float_type() {}
void inc() { value += 1; }
private:
float value = 0;
};
void dyn_test() {
std::vector<std::unique_ptr<value_type>> v;
for (int i = 0; i < 1024; i++) {
if (i % 2 == 0)
v.emplace_back(new int_type());
else
v.emplace_back(new float_type());
}
for (int i = 0; i < 900000; i++) {
std::for_each(v.begin(), v.end(), [](auto &item) { item->inc(); });
}
}
struct visitor : boost::static_visitor<> {
template <typename T> void operator()(T &item) { item += 1; }
};
using mytype = boost::variant<int, float>;
void static_test() {
std::vector<mytype> v;
for (int i = 0; i < 1024; i++) {
if (i % 2 == 0)
v.emplace_back(0);
else
v.emplace_back(0.f);
}
visitor vi;
for (int i = 0; i < 900000; i++) {
std::for_each(v.begin(), v.end(), boost::apply_visitor(vi));
}
}
template <typename F> double measure(F f) {
clock_t start = clock();
f();
clock_t end = clock();
float seconds = (float)(end - start) / CLOCKS_PER_SEC;
return seconds;
}
int main() {
std::cout << "polymorphism: " << measure([] { dyn_test(); }) << std::endl;
std::cout << "boost::variant: " << measure([] { static_test(); }) << std::endl;
return 0;
}
assembler
gcc
clang+llvm
Clang is known to miscompile some std::vector functions from various Standard libraries, due to some edge cases in their inliner. I don't know if those have been fixed by now but quite possibly not. Since unique_ptr is smaller and simpler than boost::variant it's more likely that it does not trigger these edge cases.
The code you post is practically "Why boost::variant is great". A dynamic allocation and random pointer index in addition to the regular indirections that both perform? That's a heavy hit (relatively).