到每个数组索引的最小丢失的非负整数

给定大小为N的数组arr [] ，每个数组索引的任务是找到直到给定数组的索引为止最小的缺失非负整数。

例子：

Input: arr[] = {1, 3, 0, 2}
Output: 0 0 2 4
Explanation:
Smallest missing non-negative integer from index 0 to 0 is 0.
Smallest missing non-negative integer from index 0 to 1 is 0.
Smallest missing non-negative integer from index 0 to 2 is 2.
Smallest missing non-negative integer from index 0 to 3 is 4.

Input: arr[] = {0, 1, 2, 3, 5}
Output: 1 2 3 4 4

方法：可以使用哈希解决此问题。请按照以下步骤解决问题：

• 初始化一个变量，例如smNonNeg，以在给定数组的起始索引和当前索引之间存储最小的缺少的非负整数。
• 初始化一个数组，用hash [N]来检查在起始索引和当前索引之间是否存在smNonNeg 。
• 遍历给定的数组，并检查hash [smNonNeg]是否等于0 。如果发现为真，则打印smNonNeg的值。
• 否则，在hash [smNonNeg]不等于0的同时增加smNonNeg的值。

下面是上述方法的实现：

C++

// C++ program to implement
// the above approach
 
#include 
using namespace std;
 
// Function to print the smallest
// missing non-negative integer
// up to every array indices
void smlstNonNeg(int arr[], int N)
{
    // Stores the smallest missing
    // non-negative integers between
    // start index to current index
    int smNonNeg = 0;
 
    // Store the boolean value to check
    // smNonNeg present between start
    // index to each index of the array
    bool hash[N + 1] = { 0 };
 
    // Traverse the array
    for (int i = 0; i < N; i++) {
 
        // Since output always lies
        // in the range[0, N - 1]
        if (arr[i] >= 0 and arr[i] < N) {
            hash[arr[i]] = true;
        }
 
        // Check if smNonNeg is
        // present between start index
        // and current index or not
        while (hash[smNonNeg]) {
            smNonNeg++;
        }
 
        // Print smallest missing
        // non-negative integer
        cout << smNonNeg << " ";
    }
}
 
// Driver Code
int main()
{
    int arr[] = { 0, 1, 2, 3, 5 };
    int N = sizeof(arr) / sizeof(arr[0]);
    smlstNonNeg(arr, N);
}

Java

// Java program to implement
// the above approach
import java.io.*;
import java.util.Arrays;
 
class GFG{
  
// Function to print the smallest
// missing non-negative integer
// up to every array indices
static void smlstNonNeg(int arr[], int N)
{
     
    // Stores the smallest missing
    // non-negative integers between
    // start index to current index
    int smNonNeg = 0;
  
    // Store the boolean value to check
    // smNonNeg present between start
    // index to each index of the array
    Boolean[] hash = new Boolean[N + 1];
    Arrays.fill(hash, false);
 
    // Traverse the array
    for(int i = 0; i < N; i++)
    {
         
        // Since output always lies
        // in the range[0, N - 1]
        if (arr[i] >= 0 && arr[i] < N)
        {
            hash[arr[i]] = true;
        }
  
        // Check if smNonNeg is
        // present between start index
        // and current index or not
        while (hash[smNonNeg])
        {
            smNonNeg++;
        }
  
        // Print smallest missing
        // non-negative integer
        System.out.print(smNonNeg + " ");
    }
}
  
// Driver Code
public static void main (String[] args)
{
    int arr[] = { 0, 1, 2, 3, 5 };
    int N = arr.length;
     
    smlstNonNeg(arr, N);
}
}
 
// This code is contributed by sanjoy_62

Python3

# Python3 program to implement
# the above approach
 
# Function to prthe smallest
# missing non-negative integer
# up to every array indices
def smlstNonNeg(arr, N):
     
    # Stores the smallest missing
    # non-negative integers between
    # start index to current index
    smNonNeg = 0
 
    # Store the boolean value to check
    # smNonNeg present between start
    # index to each index of the array
    hash = [0] * (N + 1)
 
    # Traverse the array
    for i in range(N):
 
        # Since output always lies
        # in the range[0, N - 1]
        if (arr[i] >= 0 and arr[i] < N):
            hash[arr[i]] = True
 
        # Check if smNonNeg is
        # present between start index
        # and current index or not
        while (hash[smNonNeg]):
            smNonNeg += 1
 
        # Print smallest missing
        # non-negative integer
        print(smNonNeg, end = " ")
 
# Driver Code
if __name__ == '__main__':
     
    arr = [ 0, 1, 2, 3, 5 ]
    N = len(arr)
     
    smlstNonNeg(arr, N)
 
# This code is contributed by mohit kumar 29

C#

// C# program to implement
// the above approach
using System;
  
class GFG{
   
// Function to print the smallest
// missing non-negative integer
// up to every array indices
static void smlstNonNeg(int[] arr, int N)
{
     
    // Stores the smallest missing
    // non-negative integers between
    // start index to current index
    int smNonNeg = 0;
   
    // Store the boolean value to check
    // smNonNeg present between start
    // index to each index of the array
    bool[] hash = new bool[N + 1];
     
    for(int i = 0; i < N; i++)
    {
        hash[i] = false;
    }
     
    // Traverse the array
    for(int i = 0; i < N; i++)
    {
         
        // Since output always lies
        // in the range[0, N - 1]
        if (arr[i] >= 0 && arr[i] < N)
        {
            hash[arr[i]] = true;
        }
   
        // Check if smNonNeg is
        // present between start index
        // and current index or not
        while (hash[smNonNeg])
        {
            smNonNeg++;
        }
   
        // Print smallest missing
        // non-negative integer
        Console.Write(smNonNeg + " ");
    }
}
   
// Driver Code
public static void Main ()
{
    int[] arr = { 0, 1, 2, 3, 5 };
    int N = arr.Length;
      
    smlstNonNeg(arr, N);
}
}
 
// This code is contributed by code_hunt

输出：

1 2 3 4 4

时间复杂度： O(N)
辅助空间： O(N)