# Duplicates in an Array

### Finding Duplicates in a Sorted Array:

```c
void findDuplicates(int a[], int n) {

    int lastDuplicate = 0;
    printf("Duplicates in the array :\n");

    for (int i = 0; i < n; i++) {
        // If two or more same elements appear consecutively
        if (a[i] == a[i+1] && lastDuplicate != a[i]) {
            printf("%d\t", a[i]);
            // Keeping track of latest duplicate to avoid
            // printing the same duplicate again
            lastDuplicate = a[i];
        }
    }
    printf("\n");
    
}
```

### Counting Duplicates in a Sorted Array:

```c
void countDuplicates(int a[], int n) {

    int j;
    printf("Duplicates in the array :\n");

    for (int i = 0; i < n-1; i++) {
        if (a[i] == a[i+1]) {
            // Start counting duplicates from i + 1
            j = i + 1;
            while (a[i] == a[j]) {
                // Finding the number of duplicates
                j++;
            }
            printf("%d is appearing %d times\n", a[i], j-i);
            // Start looking for duplicates again
            i = j - 1; 
        }    
    }

}
```

### Using Hash Array:

```c
void findAndCountDuplicates(int a[], int n, int high) {

    // Creating a hash array and initializing with 0
    // Size of hash array = maximum element in input array
    int h[high];
    for (int i = 0; i < high; i++) {
        h[i] = 0;
    }
    
    // Incrementing hash table values as per the numbers in
    // original input array
    for (int i = 0; i < n; i++) {
        h[a[i]]++;
    }
    
    // If any element in hash table has value > 1,
    // it means that the element is repeated
    for (int i = 0; i <= high; i++) {
        if (h[i] > 1) {
            printf("%d appears %d times\n", i, h[i]);
        }
    }

}
```

Contributed by Nitin Ranganath


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://nitinranganath.gitbook.io/data-structures/arrays/duplicates-in-an-array.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.