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Why this code does not work?

May 30, 2013 at 1:05pm
Observer (115)
Hi

Why this code does not work?

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  std::vector<int>::iterator itMinElem = std::find(inputArr.begin(),
            inputArr.end(), minElem);


Output:
error: conversion from '__gnu_cxx::__normal_iterator<const int*, std::vector<int> >' to non-scalar type 'std::vector<int>::iterator {aka __gnu_cxx::__normal_iterator<int*, std::vector<int> >}' requested

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/* 
 * File:   CHomework.cpp
 * Author: Ivan
 * 
 * Created on May 30, 2013, 1:51 PM
 */

#include <algorithm>
#include "CHomework.h"

void CHomework::homework(const std::vector<int>& inputArr,
        int& sum,
        int& product) throw (std::out_of_range) {

    sum = 0;
    product = 1;

    // Generate an exception if the input data is out of range
    for (std::size_t i = 0; i < inputArr.size(); i++) {
        if ((inputArr[i] < -100) || (inputArr[i] > 100)) {
            throw std::out_of_range("Input out of range: [-100, 100]");
        }
    }

    // Find the sum of the positive elements of the array
    for (std::size_t i = 0; i < inputArr.size(); i++) {
        if (inputArr[i] > 0) {
            sum += inputArr[i];
        }
    }
    
    // Find product between the first maximum and minimum elements of an array

    int minElem = *std::min_element(inputArr.begin(), inputArr.end());
    int maxElem = *std::max_element(inputArr.begin(), inputArr.end());
    
    std::vector<int>::iterator itMinElem = std::find(inputArr.begin(),
            inputArr.end(), minElem);
//    std::vector<int>::iterator itMaxElem = std::find(inputArr.begin(),
//            inputArr.end(), maxElem);
//    
//    if (itMinElem == itMaxElem) {
//        product = 0;
//        return;
//    }
//    
//    std::vector<int>::iterator itBeginProduct;
//    std::vector<int>::iterator itEndProduct;
//    if (itMinElem < itMaxElem) {
//        itBeginProduct = itMinElem;
//        itEndProduct = itMaxElem;
//    }
//    else {
//        itBeginProduct = itMaxElem;
//        itEndProduct = itMinElem;
//    }
//    
//    for (std::vector<int>::iterator it = itBeginProduct+1;
//            it < itEndProduct; it++) {
//        product *= *it;
//    }
}


But it works:
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/* 
 * File:   main.cpp
 * Author: Ivan
 *
 * Created on May 29, 2013, 4:52 PM
 */

// find example
#include <iostream>     // std::cout
#include <algorithm>    // std::find
#include <vector>       // std::vector

int main() {
    std::vector<int> inputArr;

    inputArr.push_back(-7);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int minElem = *std::min_element(inputArr.begin(), inputArr.end());
    int maxElem = *std::max_element(inputArr.begin(), inputArr.end());

    std::vector<int>::iterator itMinElem = std::find(inputArr.begin(),
            inputArr.end(), minElem);
}
Edit & run on cpp.sh
May 30, 2013 at 1:12pm
kooth (746)
Maybe because your homework() function has its parameter as a const?
May 30, 2013 at 1:23pm
Observer (115)
Yes, you're right! But I have not changed anything ... Now I'll know. Thank you!
Last edited on May 30, 2013 at 1:24pm
May 30, 2013 at 1:26pm
LB (13399)
You should use ::const_iterator instead of ::iterator ;)
May 30, 2013 at 1:30pm
Observer (115)
This is Excellent! I'll try it. Thanks!
May 30, 2013 at 1:39pm
Observer (115)
And now another error. Help please!

Output:
39: undefined reference to `CHomework::homework(std::vector<int, std::allocator<int> > const&, int&, int&)'

For each line:
 
 
CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));



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/*
 * File:   newtestclass.cpp
 * Author: Ivan
 *
 * Created on May 30, 2013, 2:02:10 PM
 */

#include "newtestclass.h"
#include "../CHomework.h"


CPPUNIT_TEST_SUITE_REGISTRATION(newtestclass);

newtestclass::newtestclass() {
}

newtestclass::~newtestclass() {
}

void newtestclass::setUp() {
}

void newtestclass::tearDown() {
}

void newtestclass::testHomework_01() {
    std::vector<int> inputArr;

    inputArr.push_back(-7);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));

    int expectedSum = 17;
    int expectedProduct = -15;

    CPPUNIT_ASSERT_EQUAL(expectedSum, sum);
    CPPUNIT_ASSERT_EQUAL(expectedProduct, product);
}

void newtestclass::testHomework_02() {
    std::vector<int> inputArr;

    inputArr.push_back(3);
    inputArr.push_back(14);
    inputArr.push_back(-9);
    inputArr.push_back(4);
    inputArr.push_back(-5);
    inputArr.push_back(1);
    inputArr.push_back(-12);
    inputArr.push_back(4);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));

    int expectedSum = 26;
    int expectedProduct = 180;

    CPPUNIT_ASSERT_EQUAL(expectedSum, sum);
    CPPUNIT_ASSERT_EQUAL(expectedProduct, product);
}

void newtestclass::testHomework_03() {
    std::vector<int> inputArr;

    inputArr.push_back(-5);
    inputArr.push_back(1);
    inputArr.push_back(2);
    inputArr.push_back(3);
    inputArr.push_back(4);
    inputArr.push_back(5);
    inputArr.push_back(6);
    inputArr.push_back(7);
    inputArr.push_back(8);
    inputArr.push_back(-3);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));

    int expectedSum = 36;
    int expectedProduct = 5040;

    CPPUNIT_ASSERT_EQUAL(expectedSum, sum);
    CPPUNIT_ASSERT_EQUAL(expectedProduct, product);
}

void newtestclass::testHomework_MinAndMaxAreLocatedNear() {
    std::vector<int> inputArr;

    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(-7);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));

    int expectedSum = 17;
    int expectedProduct = 0;

    CPPUNIT_ASSERT_EQUAL(expectedSum, sum);
    CPPUNIT_ASSERT_EQUAL(expectedProduct, product);
}

void newtestclass::testHomework_THROW_lowBound() {
    std::vector<int> inputArr;

    inputArr.push_back(-101);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_THROW(cHomework.homework(inputArr, sum, product),
            std::out_of_range);
}

void newtestclass::testHomework_NO_THROW_lowBound() {
    std::vector<int> inputArr;

    inputArr.push_back(-100);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));
}

void newtestclass::testHomework_THROW_highBound() {
    std::vector<int> inputArr;

    inputArr.push_back(101);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_THROW(cHomework.homework(inputArr, sum, product),
            std::out_of_range);
}

void newtestclass::testHomework_NO_highBound() {
    std::vector<int> inputArr;

    inputArr.push_back(100);
    inputArr.push_back(5);
    inputArr.push_back(-1);
    inputArr.push_back(3);
    inputArr.push_back(9);

    int sum;
    int product;
    CHomework cHomework;

    CPPUNIT_ASSERT_NO_THROW(cHomework.homework(inputArr, sum, product));
}
May 30, 2013 at 1:41pm
Zhuge (4664)
I would guess that you have failed to provide a definition for CHomework::homework().
May 30, 2013 at 1:44pm
Observer (115)
I do not see an error.

CHomework.h
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/* 
 * File:   CHomework.h
 * Author: Ivan
 *
 * Created on May 30, 2013, 1:51 PM
 */

#ifndef CHOMEWORK_H
#define	CHOMEWORK_H

#include <stdexcept>
#include <vector>

/**
 * Implementation of the class CHomework
 */
class CHomework {
public:
    /**
     * Returns the sum and the product from the input array
     * 
     * @param inputArr The input array with the
     * elements from the range [-100, 100]
     * @param sum The sum of the positive elements of the array
     * @param product The product numbers arranged between the
     * minimum and maximum elements
     */
    void homework(std::vector<int>& inputArr,
            int& sum,
            int& product) throw(std::out_of_range);
};

#endif	/* CHOMEWORK_H */


CHomework.cpp
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/* 
 * File:   CHomework.cpp
 * Author: Ivan
 * 
 * Created on May 30, 2013, 1:51 PM
 */

#include <algorithm>
#include "CHomework.h"

void CHomework::homework(std::vector<int>& inputArr,
        int& sum,
        int& product) throw (std::out_of_range) {

    sum = 0;
    product = 1;

    // Generate an exception if the input data is out of range
    for (std::size_t i = 0; i < inputArr.size(); i++) {
        if ((inputArr[i] < -100) || (inputArr[i] > 100)) {
            throw std::out_of_range("Input out of range: [-100, 100]");
        }
    }

    // Find the sum of the positive elements of the array
    for (std::size_t i = 0; i < inputArr.size(); i++) {
        if (inputArr[i] > 0) {
            sum += inputArr[i];
        }
    }
    
    // Find product between the first maximum and minimum elements of an array

    int minElem = *std::min_element(inputArr.begin(), inputArr.end());
    int maxElem = *std::max_element(inputArr.begin(), inputArr.end());
    
    std::vector<int>::iterator itMinElem = std::find(inputArr.begin(),
            inputArr.end(), minElem);
    std::vector<int>::iterator itMaxElem = std::find(inputArr.begin(),
            inputArr.end(), maxElem);
    
    if (itMinElem == itMaxElem) {
        product = 0;
        return;
    }
    
    std::vector<int>::iterator itBeginProduct;
    std::vector<int>::iterator itEndProduct;
    if (itMinElem < itMaxElem) {
        itBeginProduct = itMinElem;
        itEndProduct = itMaxElem;
    }
    else {
        itBeginProduct = itMaxElem;
        itEndProduct = itMinElem;
    }
    
    for (std::vector<int>::iterator it = itBeginProduct+1;
            it < itEndProduct; it++) {
        product *= *it;
    }
}
May 31, 2013 at 4:47am
Observer (115)
I'm currently using ::const_iterator instead of ::iterator. Everything is working. Thank you all :)

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void CHomework::homework(const std::vector<int>& inputArr,
        int& sum,
        int& product) throw (std::out_of_range) {

    ...
    std::vector<int>::const_iterator itMinElem = std::find(inputArr.begin(),
            inputArr.end(), minElem);
    std::vector<int>::const_iterator itMaxElem = std::find(inputArr.begin(),
            inputArr.end(), maxElem);
    ...

    ...
    std::vector<int>::const_iterator itBeginProduct;
    std::vector<int>::const_iterator itEndProduct;
    ...

    ...
    for (std::vector<int>::const_iterator it = itBeginProduct+1;
            it < itEndProduct; it++) {
        product *= *it;
    }
}
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