Break for loop after vector's last element

**hss1194** · 01-30-2013

I have a double for loop that helps me determine the highest sum in a block of numbers inside a text file. All the numbers are inputted into a vector, but eventually the vector reaches its end, and if the code goes past, I get a "vector subscript out of range" error.

I need to know how to break the for loops if it passes the vector's last element.

Code:

#include<iostream>
#include<conio.h>
#include"U:\C++\WordClass2\WordClass2\WordClass.cpp"
#include<fstream>
#include<vector>
using namespace std;


int main()
{
    WordClass pie;
    int blocksize, temp=0;
    ifstream inFile;
    inFile.open("numbers.txt");
    int numero;
    vector<int> number;
    vector<int> returner;
    while(inFile>>numero)
    {
        number.push_back(numero);
    }
    cout<<"Enter block size: ";
    cin>>blocksize;
    for(int i=0; i<number.size(); i++)        //NEED THE FUNCTION IN THIS AREA
    {
        for(int j=0; j<blocksize; j++)
        {
            temp+=number[i];
            i++;
        }
        returner.push_back(temp);
        temp=0;
        i=i-blocksize;
    }
    int killer=0, queen=0, save=0;
    for(int i=0; i<returner.size(); i++)
    {
        killer=returner[i];
        if(killer>queen)
        {
            queen=killer;
            save=i+1;
        }
    }
    cout<<endl<<"The biggest sum of numbers is: "<<queen<<endl;
    cout<<"This sum occurs at block #"<<save<<endl;
    getch();
    return 0;
}

**Salem** · 01-31-2013

Code:

        for(int j=0; j<blocksize; j++)
        {
            temp+=number[i];
            i++;
        }

The problem is, you're messing around with the other loops control variable, and not checking the range.

Try say

Code:

        for(int j=0, k = i ; j<blocksize && k < number.size() ; j++, k++ )
        {
            temp+=number[k];
        }

**Elkvis** · 01-31-2013

I've done something like this before

Originally Posted by hss1194

Code:

    [&]()
    {
      for(int i=0; i<number.size(); i++)        //NEED THE FUNCTION IN THIS AREA
      {
          for(int j=0; j<blocksize; j++)
          {
              temp+=number[i];
              // if you need to break from here, simply return
              i++;
          }
          returner.push_back(temp);
          temp=0;
          i=i-blocksize;
      }
    }();

if you have a C++11 compiler, you can simply put that in place of your nested for loop, and returning from the lambda will break out of both loops

**hk_mp5kpdw** · 01-31-2013

Code:

if(killer>queen)
{
    queen=killer;

You're not a Queen fan by any chance are you? Just curious.

**msh** · 02-01-2013

Had some fun with iterators.

I think the sub-sum part came out very neat. Disregarding the ugly conditional inclusions...

Code:

#include <iostream>
#include <fstream>
#include <vector>
#include <utility>
#include <algorithm>


#if __cplusplus < 199711L
#error "It looks like you're using an antiquated compiler. Would you like help?"
#endif


bool cmp(const std::pair<int, int> &p1, const std::pair<int, int> &p2)
{
    return (p1.second < p2.second);
}


int main()
{
    std::ifstream file;
    file.open("numbers.txt");
    if (!file) {
        std::cerr << "!> could not open input file" << std::endl;
        return 1;
    }
    
    std::vector<int> numbers;
    int a;
    while (file >> a)
        numbers.push_back(a);
    
    int block_size;
    std::cout << "Enter block size: ";
    std::cin >> block_size;
    if (block_size <= 0 || block_size > numbers.size())
        block_size = numbers.size();
    
    #if __cplusplus >= 201103L
    std::vector<std::pair<int, int>> block_sums;
    auto iter = numbers.begin();
    #elif __cplusplus >= 199711L
    std::vector<std::pair<int, int> > block_sums;
    std::vector<int>::iterator iter = numbers.begin();
    #endif
    int block_sum;
    while (numbers.end() - iter >= block_size) {
        block_sum = 0;
        for (int i = 0; i < block_size; ++i) {
            block_sum += *(iter + i);
        }
        #if __cplusplus >= 201103L
        auto pair = std::make_pair(iter - numbers.begin(), block_sum);
        #elif __cplusplus >= 199711L
        std::pair<int, int> pair;
        pair = std::make_pair(iter - numbers.begin(), block_sum);
        #endif
        block_sums.push_back(pair);
        iter++;
    }
    
    
    #if __cplusplus >= 201103L
    for (const auto &pair : block_sums)
        std::cout << "(" << pair.first << "; "
                         << pair.second << ")"
                         << std::endl;
    #elif __cplusplus >= 199711L
    std::vector<std::pair<int, int> >::iterator sums_iter;
    for (sums_iter = block_sums.begin();
         sums_iter != block_sums.end(); sums_iter++) {
        std::cout << "(" << sums_iter->first << "; "
                         << sums_iter->second << ")"
                         << std::endl;
         
    }
    #endif
    
    #if __cplusplus >= 201103L
    auto max_at = std::max_element(block_sums.begin(), block_sums.end(), cmp);
    #elif __cplusplus >= 199711L
    std::vector<std::pair<int, int> >::iterator max_at;
    max_at = std::max_element(block_sums.begin(), block_sums.end(), cmp);
    #endif
    std::cout << "Greatest sum: "
              << max_at->second
              << " @ "
              << max_at->first
              << std::endl;
}

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