trjhtr

Two Sum Problem:

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

Code:

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* twoSum(int* nums, int numsSize, int target)
 int *a = malloc(sizeof(int) * 2);
 for(int i = 0; i < numsSize; i++)
 for(int j = i+1; j < numsSize; j++)
 if (nums[i] + nums[j] == target)
 a[0] = i;
 a[1] = j;
 return a;
 
 
 
 /* Error: control reaches end of non-void function [-Werror=return-type] */

I would have done this:

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
#define INVALID (-1)
int* twoSum(int* nums, int numsSize, int target)

 int *result = malloc(sizeof(int) * 2);
 memset (result, INVALID, sizeof(int) * 2);
 for(int left = 0; left < numsSize && result[0] == INVALID; left++)
 
 for(int right = left+ 1; right < numsSize && result[0] == INVALID; right++)
 
 if (nums[left] + nums[right] == target)
 
 result[0] = left;
 result[1] = right;
 /* A return statement here instead of the overhead of the 
 second check in the for loop conditions may be a good
 idea, it depends if the driving factor is performance
 or maintainability */
 
 
 
 return result;
 

Since this is an interview question and you are showing what a shining star you are you might want to consider the following points:

• Its best to avoid multiple return points if you can, but there is
  going to be a performance hit. By adding the comment I think I have
  shown that I have identified that issue and, right or wrong, made a
  decision and explained why.




• Setting the results as early as possible may be a waste of a few
  processor cycles but it will help when the code goes wrong, you know
  you are going to have random values sneaking out, imagine what would
  happen if results[0] = 5;




• Using single letter variables means you have to right more
  comments/documents to explain your code. This is an interview
  question, you don't want to submit a 20 page document detailing what
  a, i, j mean and their range of values do you. (left and right are
  not very descriptive names, but they are better than i and j).

All I did was add one line and polish the turd a bit, which is much easier when I'm not being interviewed, good luck !