c++ Faliure on vector at runtime: vector subscript out of range

user_17943704 0
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im gettin this really annoying error message. I know Im only new to this but it seems the type of thing I could figure out. Can anyone show me where im going wrong please?

The message at run time is: Debug Assertion Failed! Program: .... File: c:\program files\microsoft visual studio 10.0\vc\include\vector Line: 932 Expression: Vector subscript out of range

and the code is

#include<iostream>
#include<vector>
using namespace std;

struct Things {
    string name;
    string color;
    string poison;
    string burns;
    double height;
};

typedef vector<Things> Forest;

void read_data(Forest& v) {
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cout << "DINTRE" << endl;
        cin >> v[i].name;
        cout << v[i].name << endl;
    }

}

int count(const Forest& v, string name, string color, string poison, string burns, double height) {
    int x = v.size();
    int cont = 0;
    for (int i = 0; i < x; ++i) {
        if (v[i].name == name or name == "*") {
            if (v[i].color == color or color == "*") {
                if (v[i].poison == poison or poison == "*") {
                    if (v[i].burns == burns or burns == "*") {
                        if (v[i].height >= height or height == 0) ++cont;
                    }
                }
            }
        }
    }
    return cont;
}

int main() {
    Forest v;
    read_data(v);
    vector<string> pregunta(4);
    while (cin >> pregunta[0]) {
        for (int i = 1; i < 4; ++i) {
            cin >> pregunta[i];
        }
        double height;
        cin >> height;
        cout << count(v, pregunta[0], pregunta[1], pregunta[2], pregunta[3], height) << endl;
    }
}
assertion vector c++
3 Answers

In read_data you access the std::vector<Things> (Forest) v out of bounds (out of range) since the vector is empty.

You could resize it after having asked the user for how many elements that should be entered.

Example:

void read_data(Forest& v) {
    int n;

    if(std::cin >> n && n > 0) v.resize(n);   // resize

    for (int i = 0; i < v.size(); ++i) {      // use v.size() here
        std::cout << "DINTRE\n";
        std::cin >> v[i].name;
        std::cout << v[i].name << '\n';
    }
}

or simpler by using a range-based for loop:

void read_data(Forest& v) {
    int n;

    if(std::cin >> n && n > 0) v.resize(n);

    for(auto& thing : v) {
        std::cout << "DINTRE\n";
        std::cin >> thing.name;
        std::cout << thing.name << '\n';
    }
}
user_75822470

consider the first line that tries to modify the data in v:

cin >> v[i].name;

This is occurring while v is an empty vector (has a size of 0). To add elements to the end of a vector you need to use push_back:

string name;
cin >> name;
v.push_back(name);

the square brackets ("[]") are for accessing an element that already exists in the vector.

user_179424470

The size of vector, passed in read_data(), is 0 i.e. it's an empty vector. In read_data(), when you doing v[i] that means you are trying to access ith element of vector v which does not exists. Hence, you are getting the error. To fix this, create an object of type Things, take user input and push_back() it in vector v:

    for (int i = 0; i < n; ++i) {
        Things x;
        cout << "DINTRE" << endl;
        cin >> x.name;
        cout << x.name << endl;
        v.push_back(x);
    }
user_85423460
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