LeetCode Two Sum Solution Explained - Java

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[basedecho]

So much respect for you. You documented your grind from start to finish!

[AnshumanBiswas]

Thanks, Nick! I think the reason why the execution takes more time at the end of the video is that you are performing the subtraction operation twice, rather than perform it once and only retrieve the value in two places. The original approach you showed is more efficient and the Leetcode compiler seems to agree.

[Shiva-zyjq]

Thanks. I am gonna watch all your leetcode videos and give thumbs up to all the videos :)

[tarunmendon]

Put "int complement=0" out of the for loop. You would get the output in 1 ms

[cyrilpatton]

One thing to note: given that nums[i] is the key, if the test array (nums) has duplicate values e.g: [1, 1, 1, 14, 3, 7, 2], you will get an error for adding a new value to the hashmap with a key that already exists. Better to do num_map.put(i, nums[i])

[lucaspenz]

It is faster to keep the subtraction into a var because it only needs to calculate once

[saileshramesh]

Thank-you so much I just started learning DSA, your videos are very helpful and your doing a great job.

[itheblackwolfofmyfamily]

Man you look like big head from Silicon Valley movie series. Good work! Thank you for the video

[ProdHway]

Is compliment the same as saying answer? I'm confused on why we use that word

[prakashkrishna]

Brute Force Solution:

class Solution {
public int[] twoSum(int[] nums, int target) {
int first, comp;
for(int i=0;i<nums.length;i++){
for(int j=i+1;j<nums.length;j++){
if(nums[i] + nums[j] == target){
int[] ans = {i, j};
return ans;
}
}
}
return nums;
}
}

[Thephantom]

Thank you so much. You taught me how to solve this and now I know how to use hashmaps.

[theindecisivegamer]

i keep running into missing return statment for line 15. Thanks for this video too i understand the algorithm very well. I seem to run into same problem with return statments in all my code .

[annieonee]

Why can't we put the num_map.put(nums[i], i) at the beginning of the for loop? I tried that and it gives runtime error for the input [3, 3]. But if I put it at the end of the for loop like in the video, it's good

[saumyasingh]

Thanks from India!
You really explain very well :)

[rohitsakalle]

There is a issue in this code now based on newly test added, that what if you have duplicate items in array for example 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1 and target is 11

[surajyerramilli]

do I Need to write IllegalArgumentException or can i just have a print statement that says "no match found"

[Priyanka-xhgs]

in the nested for loop solution, if you remove the throw newIllegal line since it isnt needed, then you get an error that says 'missing return statement', how do you resolve that error in a manner that does not have redundant code. Thank you in advance!

[ShadwBXr]

could anyone explain to me how the section: compliment = target - nums[i] works?

[theweird_]

why did we go nums.length in the second loop wouldn't there be an error of index outof bounds

[Mkm-xthx]

Hi I have a question on:

return int[] {num_map.get(complement), i}

How does it not return [1, 0], since the complement is in index 1 (7) and i is still index 0 (2)

Appreciate the video and help