如何在C++向量中奇数元素前面加上值-1，我在使用insert函数时遇到了问题

How do I add the value -1 in front of odd numbered elements in a C++ vector, I have problems using the insert function

本文关键字：insert 问题 遇到 函数 向量 C++ 前面 元素      更新时间：2023-10-16
int main ()
{
vector < int  > v;
v = initialize (v);
cout << "Initial Vector: " << endl;
print (v);
cout << "Adding -1 in front of Odds: " << endl;
v = insert_odds(v);
cout << "Final Vector: " << endl;
print(v);
}
double random (unsigned int &seed)
{
const int MODULUS = 15749;
const int MULTIPLIER = 69069;
const int INCREMENT = 1;
seed = ((MULTIPLIER * seed) + INCREMENT) % MODULUS;
return double (seed) / double (MODULUS);
}
vector <int > initialize (vector < int > v)
{
unsigned int seed=2;
for (int i = 0; i < 10; i++)
v.push_back(int (10 + (10 * random (seed))));
return v;
}
void print (vector < int > v)
{
for (int i = 0; i < v.size(); i++)
cout << v[i] << " ";
cout << endl;
}
bool isOdd(int n)
{
return n%2 != 0 && n > 0;
}
vector<int> insert_odds(vector <int> v)
{
std::vector<int>::iterator it = find_if(v.begin(),v.end(),isOdd);
while(it  != v.end())
{
it = find_if(v.begin(),v.end(),isOdd);
v.insert(it,-1);
}
return v;
}

这是我的密码。开头的矢量是17 10 14 16 15 19 19 10 14 18我希望输出-1 17 10 14 16-1 15-1 19-1 19 10 14 18

截至目前，程序正在运行，但没有输出。

如果您想在迭代向量时将新元素插入到向量中，您有两个选择：

  1. 使用insert()返回的iterator：

    vector<int>::iterator iter = myVector.begin();
while (iter != myVector.end())
{
if ((*iter % 2) != 0)
iter = myVector.insert(iter, -1) + 2;
else
++iter;
}

  2. 使用索引而不是迭代器：

    vector<int>::size_type idx = 0;
while (idx < myVector.size())
{
if ((myVector[idx] % 2) != 0)
{
myVector.insert(myVector.begin()+idx, -1);
idx += 2;
}
else
++idx;
}

使用vector::insert():的返回值

vector<int> v = { 1, 2, 3, 4, 5 };
for (auto it = v.begin(); it != v.end(); it++)
{
if (*it & 1)
{
it = v.insert(it, -1);
it++;
}
}
相关文章：