Two Sum

shriyanshi24jindal

Mar 30th, 2026

134

Never

Not a member of GistPad yet? Sign Up, it unlocks many cool features!

Java 8.19 KB | None | 0 0

copy raw download clone embed print report

class Solution {
/** Bruite force, O(N) O(N) */
public int[] twoSum(int[] nums, int target) {
int[] arr = new int[]{-1,-1};
Map<Integer, Integer> map = new HashMap<>();
for(int i=0; i <nums.length; i++)
{
int diff = target - nums[i];
if(map.containsKey(diff))
{
arr[0] = map.get(diff);
arr[1] = i;
break;
}
else
map.put(nums[i], i);
}
return arr;
}
/** Two pointer approach, O(N) O(1) */
// works only if array has positive elements
public int[] twoSum(int[] nums, int target) {
int i=0;
int j=nums.length-1;
int[] arr = new int[]{-1,-1};
while(i < j)
{
if(nums[i] + nums[j] == target)
{
arr[0] = i;
arr[1] = j;
break;
}
else if(nums[i] + nums[j] < target)
i++;
else if(nums[i] + nums[j] > target)
j--;
}
return arr;
}
}

RAW Paste Data Copied

class Solution {
    /** Bruite force, O(N) O(N) */
    public int[] twoSum(int[] nums, int target) {
        int[] arr = new int[]{-1,-1};

Map<Integer, Integer> map = new HashMap<>();

for(int i=0; i <nums.length; i++)
        {
            int diff = target - nums[i];

if(map.containsKey(diff))
            {
                arr[0] = map.get(diff);
                arr[1] = i;
                break;
            }
            else
                map.put(nums[i], i);
        }
        return arr;
    }

/** Two pointer approach, O(N) O(1) */
    // works only if array has positive elements
    public int[] twoSum(int[] nums, int target) {
        int i=0;
        int j=nums.length-1;
        int[] arr = new int[]{-1,-1};

while(i < j)
        {
            if(nums[i] + nums[j] == target)
            {
                arr[0] = i;
                arr[1] = j;
                break;
            }
            else if(nums[i] + nums[j] < target)
                i++;
            else if(nums[i] + nums[j] > target)
                j--;
        }
        return arr;
    }
}