向量和 for 不产生结果

Question

我正在玩一个简单的游戏（石头剪刀布），当我尝试使用另一个向量的元素作为条件来填充一个向量时遇到了这个问题。代码可能更容易理解：

#include "stdafx.h"
#include "../../Library/std_lib_facilities.h"

// With the fibonacci series I can generate a secret sequence of number
int fib(int n){
    if (1 == n || 2 == n) {
        return 1;
    }
    else {
        return fib(n - 1) + fib(n - 2);
    }
}

// It shows the list of element in a given vector
void showVector(vector<int>myVector, string nameVector) {
    cout << "\n\n";
    cout << nameVector << " Debug: | ";
    for (int i = 1; i < 10; i++) {
        cout << myVector[i] << " | ";
    }
    cout << "\n\n";
}

// String variant
void showVector(vector<string>myVector, string nameVector) {
    cout << "\n\n";
    cout << nameVector << " Debug: | ";
    for (int i = 1; i < 10; i++) {
        cout << myVector[i] << " | ";
    }
    cout << "\n\n";
}

// Generate a sequence of number in a vector
vector<int> generateCode(int input) {

    vector<int>myVector;

    for (int i = 1; i <= 10; i++) {
        myVector.push_back(fib(i + input) % 3);
    }

    return myVector;
}

int main()
{
    // Secret sequence of moves, based on the value (0, 1 or 2) i will show Rock, Paper or Scissor
    vector<int>fibSeries;
    vector<string>movSeries;

    // Initialization and settings
    int input = 0;

    cout << "Digit an integer to start: ";
    while (cin >> input) {

        // Check the number to make sure is a valid one (i will implement a check later) and generate the secret code
        fibSeries = generateCode(input);

        // For each 0 i'll put Rock in the vector, same for 1 ( in this case paper ) and 2 ( scissor )
        for (int i = 0; i <= fibSeries.size(); i++) {
            if (fibSeries[i] == 0){
                movSeries.push_back("Rock");
            }
            else if (fibSeries[i] == 1) {
                movSeries.push_back("Paper");
            }
            else if (fibSeries[i] == 2) {
                movSeries.push_back("Scissor");
            }
            else {
                movSeries.push_back("Rock");
            }
        }

        // Shows the vector graphically, for debug.
        showVector(fibSeries, "fibisSeries");
        showVector(movSeries, "movSeries");

        // So for a combination of      1 - 2 - 0 - 1
        // The result should be:        Paper - Scissor - Rock - Paper

    }

    return 0;
}

执行代码后，我得到一个（中止）。我不明白，我是 C++ 的新手所以如果是一个愚蠢的错误请原谅我。大多数代码都很复杂，因为我有规则要遵循，所以例如，如果我没有研究某些东西，我就不能在这里使用它。我只想知道为什么代码不希望我将 for 与向量一起使用！

Answer 1

for (int i = 0; i <= fibSeries.size(); i++)

正如@Yola 所提到的，你迭代一个元素比你拥有的多：

如果您有向量 std::vector<char> v = {'a', 'b', 'c'};，可以按以下方式访问元素：

v[0] (-> 'a')
v[1] (-> 'b')
v[2] (-> 'c')

通常，您的最大索引将为 length - 1。

for (int i = 0; i <= fibSeries.size(); i++)

从0迭代到小于或等于到size()；即 0、1、2、3（4 个元素，在 3 元素向量中）。

正确的代码应该是：

for (int i = 0; i < fibSeries.size(); i++)
                 ^^^

Answer 2

因此，如前所述，您的问题是您应该始终使用 < size，因为索引是 0-based <= size 将读取已分配 space 的末尾.

但如果可以的话，请多加评论，c++11 introduced a new style of range based for-loops 这将使您完全不必编写条件和迭代表达式：

map<int, string> movSeries = { { 0, "Rock"s }, { 1, "Paper"s }, { 2, "Scissors"s } };
vector<int> fibSeries(10);
auto input = 0;

while(cin >> input) {
    for(auto& i : fibSeries) {
        i = fib(input++) % 3;
    }

    cout << "\n\nDebug | ";
    copy(cbegin(fibSeries), cend(fibSeries), ostream_iterator<int>(cout, " | "));
    cout << "\n\n\n\nDebug | ";

    for(const auto i : fibSeries) {
        cout << movSeries[i] << " | ";
    }
    cout << endl << endl;
}

向量和 for 不产生结果

Vector and for doesn't produce results

c++

for-loop

runtime-error

vector

abort