Topic tags :- Array, Hash Table
Question type :- Easy
Question link : Two Sum
Note : Try yourself before seeing solution here.
Question :
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
You can return the answer in any order.
Example 1:
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Output: Because nums[0] + nums[1] == 9, we return [0, 1].
Example 2:
Input: nums = [3,2,4], target = 6
Output: [1,2]
Example 3:
Input: nums = [3,3], target = 6
Output: [0,1]
Constraints:
2 <= nums.length <= 104
-109 <= nums[i] <= 109
-109 <= target <= 109
Only one valid answer exists.
Follow-up: Can you come up with an algorithm that is less than O(n2) time complexity?
Solutions : in Java
Solution 1:
class Solution {
public int[] twoSum(int[] nums, int target) {
for (int i = 1; i < nums.length; i++)
for (int j = i; j < nums.length; j++)
if (nums[j] + nums[j - i] == target)
return new int[]{j - i, j};
return null;
}
}
Runtime: 1 ms
Memory Usage: 41.9 MB
Solution link : click here
Solution 2:
class Solution {
public int[] twoSum(int[] nums, int target) {
for(int i=0;i<nums.length;i++){
for(int j=1;j<nums.length;j++){
if(i==j){
continue;
}
if(nums[i]+nums[j]== target){
return new int[] {Math.min(i,j),Math.max(i,j)};
}
}
}
return nums;
}
}
Runtime: 155 ms
Memory Usage: 42 MB
Solution link : click here
Solution 3:
class Solution {
public int[] twoSum(int[] nums, int target) {
int arr[] = new int[2];
for(int i=0;i<nums.length;i++){
for(int j=1;j<nums.length;j++){
if(i==j){
continue;
}
if(nums[i]+nums[j]== target){
arr[0] = Math.min(i,j);;
arr[1] = Math.max(i,j);
return arr;
}
}
}
return arr;
}
}
Runtime: 180 ms
Memory Usage: 41.9 MB
Solution link : click here
Solution 4:
class Solution {
public int[] twoSum(int[] nums, int target) {
for(int a=0;a<nums.length;a++){
for(int b=a+1;b<nums.length;b++){
if(nums[a]+nums[b]==target)
{
return new int[] {a ,b};
}
}
}
throw new IllegalArgumentException("No two sum solution");
}
}
Runtime: 44 ms
Memory Usage: 40 MB
Solution link : click here
Thank you
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