Two Sum problem | Leetcode problem 1

Two Sum problem.
Leetcode problem number 1.

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[satyam]

Samajh kuch nhi aaya per dekh kr achha lga

[saikumarperamsetty]

brute force
to check is 2 numbers in an array adds to a particular sum

[SingWithShivansh]

class Solution {
public int[] twoSum(int[] nums, int target) {
// int[] arr = {-1, -1};
// for(int i =0; i< nums.length; i++){
// for(int j =i+1; i< nums.length; i++){
// if(nums[i] + nums[j] == target){
// arr[0] = i;
// arr[1] = j;
// }
// }
// } O(n*n)
HashMap<Integer, Integer> map = new HashMap<>();
for(int i =0; i< nums.length; i++){
int req = target-nums[i];
if(map.containsKey(req)){
int[] arr = {map.get(req), i};
return arr;
}
map.put(nums[i], i);
}
return new int[]{-1, -1};
}
}

[pnkkumar]

good explaination, but you are missing time and space complexity in this explaination.

[techrahul]

Internal working nhi smj aayi hai..how it works behind the scene??

[manjotkaur]

How to do it withour hashmaps with Time complexity O(n)

[raghuhg]

If the mode of number is zero it not palindrome this could be first check

[venkateshvenkat]

u r explained in java what abiut python

[saikumarperamsetty]

first show the program clearly end 2 end, if any one can take Screenshot of Every programs