vector<int>& nums什么意思

A vector<int> is a standard library container in C++ that holds a sequence of integer values. It is similar to an array, but provides dynamic resizing and other useful methods such as push_back(), pop_back(), size(), and clear(). The vector<int> is implemented as a template class, which means that it can be instantiated with any data type, not just int.

相关问题

vector<int>& nums)什么意思

A vector is a dynamic array in C++ that allows us to store and manipulate a collection of elements of the same data type. The vector<int> is a specific type of vector that stores integers (int). Here is an example of how we can declare and initialize a vector<int>:

#include <vector>
#include <iostream>

using namespace std;

int main() {
  // declare and initialize a vector of integers
  vector<int> myVector = {1, 2, 3, 4, 5};
  
  // print the vector elements
  for (int i = 0; i < myVector.size(); i++) {
    cout << myVector[i] << " ";
  }
  cout << endl;
  
  return 0;
}

Output:

1 2 3 4 5

In this example, we declare a vector of integers called `myVector` and initialize it with five integer values. We then use a for loop to iterate through the elements of the vector and print them to the console. The output shows the values 1, 2, 3, 4, and 5, separated by spaces.

vector<int>& nums

给定一个整数数组 nums 和一个目标值 target，请你在该数组中找出和为目标值的那两个整数，并返回他们的数组下标。

你可以假设每种输入只会对应一个答案。但是，数组中同一个元素不能使用两遍。

C++代码：

vector<int> twosum(vector<int>& nums, int target) {
    unordered_map<int, int> num_map;
    for (int i = 0; i < nums.size(); i++) {
        int complement = target - nums[i];
        if (num_map.count(complement)) {
            return { num_map[complement], i };
        }
        num_map[nums[i]] = i;
    }
    return {};
}

这段代码使用了unordered_map存储数组元素与下标的映射，然后枚举数组中的每一个元素，如果找到了和它相加等于target的元素，就返回它们的下标。否则返回空数组。