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import java.util.*;

class Solution {
    // Function to find indices of two elements whose sum equals the target
    public int[] twoSum(int[] nums, int target) {
        // Initialize two pointers at start and end
        int left = 0, right = nums.length - 1;

        // Loop until pointers cross
        while (left < right) {
            // Calculate sum at pointers
            int sum = nums[left] + nums[right];

            // If sum equals target, return 1-based indices
            if (sum == target) {
                return new int[] {left + 1, right + 1};
            }
            // If sum less than target, move left pointer forward
            else if (sum < target) {
                left++;
            }
            // If sum greater than target, move right pointer backward
            else {
                right--;
            }
        }

        // Return empty array if no pair found
        return new int[0];
    }
}

public class Main {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3, 4, 6, 8};
        int target = 10;

        Solution sol = new Solution();
        int[] res = sol.twoSum(nums, target);

        if (res.length == 2) {
            System.out.println("Indices: " + res[0] + ", " + res[1]);
        } else {
            System.out.println("No valid pair found.");
        }
    }
}

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class Solution:
    # Function to find indices of two elements whose sum equals the target
    def twoSum(self, nums, target):
        # Initialize two pointers at start and end
        left, right = 0, len(nums) - 1

        # Loop until pointers cross
        while left < right:
            # Calculate sum at pointers
            current_sum = nums[left] + nums[right]

            # If sum equals target, return 1-based indices
            if current_sum == target:
                return [left + 1, right + 1]
            # If sum less than target, move left pointer forward
            elif current_sum < target:
                left += 1
            # If sum greater than target, move right pointer backward
            else:
                right -= 1

        # Return empty list if no pair found
        return []

# Driver code
if __name__ == "__main__":
    nums = [1, 2, 3, 4, 6, 8]
    target = 10

    sol = Solution()
    res = sol.twoSum(nums, target)

    if res:
        print("Indices:", res[0], res[1])
    else:
        print("No valid pair found.")

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