c++ - Inserting an element into multi dimension vector errors -

i'm writing program i'm creating lab multidimensional vectors. far have constructor asks user input number , sizes of lab. in program i'm creating function called addlab add new lab @ specified position number of computers inputted user.

while testing program make user input number of sizes of lab 3 tried adding lab 5 vector following output doesn't compile correctly:

labs: computer stations: 1:      1:empty  2:empty  3:empty 2:      1:empty  2:empty  3:empty 3:      1:empty  2:empty  3:empty want lab inserted at? 

here header file

#ifndef __grade_weight_calculator__computerlabs__ #define __grade_weight_calculator__computerlabs__  #include <iostream> #include <string> #include <vector> using namespace std;   class computerlabs{ public:     computerlabs();     void show_labs();     void add_lab(); private:     vector<vector<string>> labs;     int numoflab;     int numofcomp;     int lab_numba;     int comp_numba; };  #endif 

here implementation cpp file

#include "computerlabs.h"  computerlabs::computerlabs() {     cout<<"input number of labs"<<endl;     cin>>numoflab;     cout<<"input size of labs"<<endl;     cin>>numofcomp;      (int i=0;i<numoflab; i++){            vector<string> row;         (int j=0;j<numofcomp; j++)             row.push_back("empty");         labs.push_back(row);     } }  void computerlabs::show_labs() {     cout<<"labs: "<<"computer stations:"<<endl;      int a=0;     int j;      (int i=0;i<numoflab; i++){         cout<<a+1<<":    ";          j=0;         while(j<numofcomp){             cout<<"  ";             cout<<j+1<<":"<<labs[i][j];             ++j;         }         a++;         cout<<endl;     } }  void computerlabs::add_lab() {     cout<<"where want lab inserted at?"<<endl;     numoflab=5;//this makes add lab 5       vector<string> row;     for(int i=0;i<numofcomp;i++)     {         row.push_back("empty");     }     labs.insert(labs.begin()+4,row);  } 

and here main.cpp file:

#include "computerlabs.h"  int main() {     computerlabs mycomp;      mycomp.show_labs();     mycomp.add_lab();     mycomp.show_labs();  } 

i think error might causing relates show_labs() function in terms of algorithm tried using im not entirely sure. can me figure out issues , solution fixing it?

the main problem in code in add_lab() function.

void computerlabs::add_lab() {     cout<<"where want lab inserted at?"<<endl;      // problem line     // not sure why needed that.     // when initial value of numoflab 3,      // numoflabs can changed 4 not 5. if set     // 5 here, run problem in show_lab() since     // there aren't 5 rows in 2d vector.     numoflab=5;//this makes add lab 5       vector<string> row;     for(int i=0;i<numofcomp;i++)     {         row.push_back("empty");     }     labs.insert(labs.begin()+4,row);  } 

change function to:

void computerlabs::add_lab() {     cout<<"where want lab inserted at?"<<endl;     int pos;     cin >> pos;      // make sure input position valid.     if ( pos > numoflab )     {        cout << "invalid position." << endl;        return;     }      // increment numoflab 1     ++numoflab;      std::vector<std::string> temprow;     for(int i=0;i<numofcomp;i++)     {        temprow.push_back("empty");     }     labs.insert(labs.begin()+pos, temprow); } 

general improvements

you don't need store numoflab in class member variable. can derived labs.

i see have updated code row not member variable of class more.

as matter of design, it's better provide class data rather expecting class data stdin or cin.

here's updated version of program.

#include <iostream> #include <string> #include <vector>  using namespace std;   class computerlabs {    public:       computerlabs(int numoflab, int numofcomp);       void show_labs();       void add_lab(int pos);    private:       vector<vector<string>> labs;       int numofcomp;       int lab_numba;       int comp_numba; };  computerlabs::computerlabs(int numoflab, int numofcomp) : numofcomp(numofcomp) {    (int = 0; < numoflab; i++){       std::vector<std::string> row;       (int j = 0; j < numofcomp; j++)       {          row.push_back("empty");       }       labs.push_back(row);    } }  void computerlabs::show_labs() {    cout << "labs: " << "computer stations:" << endl;     int numoflab = labs.size();    (int = 0; i<numoflab; i++){       cout << i+1 << ":    ";        (int j = 0; j < numofcomp; j++)       {          cout<<"  ";          cout << j+1 << ":" << labs[i][j];       }       cout<<endl;    } }  void computerlabs::add_lab(int pos) {    int numoflab = labs.size();    if ( pos < 0 || pos > numoflab )    {       cout << "invalid position." << endl;       return;    }     std::vector<std::string> row;    for(int i=0;i<numofcomp;i++)    {       row.push_back("empty");    }    labs.insert(labs.begin()+pos,row); }  int main() {    int numoflab;    int numofcomp;     cout << "input number of labs" << endl;    cin >> numoflab;    cout << "input size of labs" << endl;    cin >> numofcomp;     if (!cin )    {       // deal error.    }     computerlabs mycomp(numoflab, numofcomp);     mycomp.show_labs();     cout << "where want lab inserted at?" << endl;    int pos;    cin >> pos;    if (!cin )    {       // deal error.    }     mycomp.add_lab(pos);    mycomp.show_labs(); } 

update

if sizes of newly added labs different sizes of existing labs, can following:

1. remove numofcomp member variable.
2. add argument add_lab, numofcomp.
3. before calling add_lab, ask user number of components of lab.

#include <iostream> #include <string> #include <vector>  using namespace std;   class computerlabs {    public:       computerlabs(int numoflab, int numofcomp);       void show_labs();       void add_lab(int pos, int numofcomp);    private:       vector<vector<string>> labs; };  computerlabs::computerlabs(int numoflab, int numofcomp) {    (int = 0; < numoflab; i++){       std::vector<std::string> row;       (int j = 0; j < numofcomp; j++)       {          row.push_back("empty");       }       labs.push_back(row);    } }  void computerlabs::show_labs() {    cout << "labs: " << "computer stations:" << endl;     int numoflab = labs.size();    (int = 0; i<numoflab; i++){       cout << i+1 << ":    ";        int numofcomp = labs[i].size();       (int j = 0; j < numofcomp; j++)       {          cout<<"  ";          cout << j+1 << ":" << labs[i][j];       }       cout<<endl;    } }  void computerlabs::add_lab(int pos,                            int numofcomp) {    int numoflab = labs.size();    if ( pos < 0 || pos > numoflab )    {       cout << "invalid position." << endl;       return;    }     std::vector<std::string> row;    for(int i=0;i<numofcomp;i++)    {       row.push_back("empty");    }    labs.insert(labs.begin()+pos,row); }  int main() {    int numoflab;    int numofcomp;     cout << "input number of labs" << endl;    cin >> numoflab;    cout << "input size of labs" << endl;    cin >> numofcomp;     if (!cin )    {       // deal error.    }     computerlabs mycomp(numoflab, numofcomp);     mycomp.show_labs();     cout << "where want lab inserted at?" << endl;    int pos;    cin >> pos;    cout << "input size of lab" << endl;    cin >> numofcomp;     if (!cin )    {       // deal error.    }     mycomp.add_lab(pos, numofcomp);    mycomp.show_labs(); }