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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. int* findDuplicates(int* nums, int numsSize, int* returnSize) {
  5.     *returnSize = 0;  // Initialize the size of the result array
  6.     int* result = (int*)malloc(numsSize * sizeof(int));  // Allocate space for the result array
  7.  
  8.     for (int i = 0; i < numsSize; i++) {
  9.         int index = abs(nums[i]) - 1;  // Get the index based on the value in the array
  10.  
  11.         // If the number at that index is negative, the number has been seen before
  12.         if (nums[index] < 0) {
  13.             result[(*returnSize)++] = abs(nums[i]);  // Add the duplicate to the result array
  14.         } else {
  15.             nums[index] = -nums[index];  // Mark the number as seen by negating it
  16.         }
  17.     }
  18.  
  19.     return result;
  20. }
  21.  
  22. int main() {
  23.     int nums[] = {4, 3, 2, 7, 8, 2, 3, 1};  // Example input
  24.     int numsSize = sizeof(nums) / sizeof(nums[0]);
  25.     int returnSize;
  26.  
  27.     int* result = findDuplicates(nums, numsSize, &returnSize);  // Find duplicates
  28.  
  29.     printf("Duplicates: ");
  30.     for (int i = 0; i < returnSize; i++) {
  31.         printf("%d ", result[i]);  // Print the result
  32.     }
  33.  
  34.     free(result);  // Free the allocated memory for the result array
  35.     return 0;
  36. }
  37.  
Success #stdin #stdout 0s 5276KB
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stdin
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Standard input is empty
stdout
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Duplicates: 2 3
https://ideone.com/FgmKLd
language:
C (gcc 8.3)
created:
279 days ago
visibility:
public

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