给定范围[1, N]中的整数列表，其中缺少一些元素。任务是找到缺失的元素。请注意，列表中可能存在重复项。
例子：
Input: arr[] = {1, 3, 3, 3, 5}
Output: 2 4
Input: arr[] = {1, 2, 3, 4, 4, 7, 7}
Output: 5 6方法：在给定的范围[1, N]中，每个索引都应该有一个元素对应。如果一个元素丢失，那么它的索引将永远不会被访问。
Traverse the array:
For each element:
if array[element] > 0:
Mark the element as visited
Again, traverse the array:
if element isNot Visited:
add it as missing element下面是上述方法的实现：
C++
// C++ implementation of the approach
#include
using namespace std;
// Function to find the missing elements
vector missing_elements(vector vec)
{
// Vector to store the list
// of missing elements
vector mis;
// For every given element
for (int i = 0; i < vec.size(); i++) {
// Find its index
int temp = abs(vec[i]) - 1;
// Update the element at the found index
vec[temp] = vec[temp] > 0 ? -vec[temp] : vec[temp];
}
for (int i = 0; i < vec.size(); i++)
// Current element was not present
// in the original vector
if (vec[i] > 0)
mis.push_back(i + 1);
return mis;
}
// Driver code
int main()
{
vector vec = { 3, 3, 3, 5, 1 };
// Vector to store the returned
// list of missing elements
vector miss_ele = missing_elements(vec);
// Print the list of elements
for (int i = 0; i < miss_ele.size(); i++)
cout << miss_ele[i] << " ";
return 0;
} Java
// Java implementation of the above approach
import java.util.*;
class GFG
{
// Function to find the missing elements
static Vector missing_elements(Vector vec)
{
// Vector to store the list
// of missing elements
Vector mis = new Vector();
// For every given element
for (int i = 0; i < vec.size(); i++)
{
// Find its index
int temp = Math.abs((int)vec.get(i)) - 1;
// Update the element at the found index
if ((int)vec.get(temp) > 0)
vec.set(temp,-(int)vec.get(temp));
else
vec.set(temp,vec.get(temp));
}
for (int i = 0; i < vec.size(); i++)
{
// Current element was not present
// in the original vector
if ((int)vec.get(i) > 0)
mis.add(i + 1);
}
return mis;
}
// Driver code
public static void main(String args[])
{
Vector vec = new Vector();
vec.add(3);
vec.add(3);
vec.add(3);
vec.add(5);
vec.add(1);
// Vector to store the returned
// list of missing elements
Vector miss_ele = missing_elements(vec);
// Print the list of elements
for (int i = 0; i < miss_ele.size(); i++)
System.out.print(miss_ele.get(i) + " ");
}
}
// This code is contributed by AnkitRai01Python3
# Python3 implementation of the approach
# Function to find the missing elements
def missing_elements(vec):
# Vector to store the list
# of missing elements
mis = []
# For every given element
for i in range(len(vec)):
# Find its index
temp = abs(vec[i]) - 1
# Update the element at the found index
if vec[temp] > 0:
vec[temp] = -vec[temp]
for i in range(len(vec)):
# Current element was not present
# in the original vector
if (vec[i] > 0):
mis.append(i + 1)
return mis
# Driver code
vec = [3, 3, 3, 5, 1]
# Vector to store the returned
# list of missing elements
miss_ele = missing_elements(vec)
# Print the list of elements
for i in range(len(miss_ele)):
print(miss_ele[i], end = " ")
# This code is contributed by Mohit KumarC#
// C# implementation of the approach
using System;
using System.Collections.Generic;
class GFG
{
// Function to find the missing elements
static List missing_elements(List vec)
{
// List to store the list
// of missing elements
List mis = new List();
// For every given element
for (int i = 0; i < vec.Count; i++)
{
// Find its index
int temp = Math.Abs((int)vec[i]) - 1;
// Update the element at the found index
if ((int)vec[temp] > 0)
vec[temp] = -(int)vec[temp];
else
vec[temp] = vec[temp];
}
for (int i = 0; i < vec.Count; i++)
{
// Current element was not present
// in the original vector
if ((int)vec[i] > 0)
mis.Add(i + 1);
}
return mis;
}
// Driver code
public static void Main(String []args)
{
List vec = new List();
vec.Add(3);
vec.Add(3);
vec.Add(3);
vec.Add(5);
vec.Add(1);
// List to store the returned
// list of missing elements
List miss_ele = missing_elements(vec);
// Print the list of elements
for (int i = 0; i < miss_ele.Count; i++)
Console.Write(miss_ele[i] + " ");
}
}
// This code is contributed by 29AjayKumar Javascript
输出：
2 4时间复杂度： O(N)，其中 N 是向量vec的长度。
辅助空间： O(N)
如果您希望与专家一起参加现场课程，请参阅DSA 现场工作专业课程和学生竞争性编程现场课程。