分析

題目

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Note: • Your returned answers (both index1 and index2) are not zero-based. • You may assume that each input would have exactly one solution and you may not use the same element twice.

Example:

Input: numbers = [2,7,11,15], target = 9 Output: [1,2] Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

解答

package LeetCode;
import java.util.Arrays;

public class L167_TwoSumII_InputArraySorted {
    public int[] twoSum(int[] numbers, int target) {
        int front=0,back=numbers.length-1;
        while(numbers[front]+numbers[back]!=target){
            if(numbers[front]+numbers[back]>target)
                back--;
            else
                front++;
        }
        return new int[]{front+1,back+1};//下標計數從1開始
    }
    public static void main(String[] args){
        L167_TwoSumII_InputArraySorted l167=new L167_TwoSumII_InputArraySorted();
        int[] numbers = {2,7,11,15};
        int target = 9;
        int[] result=l167.twoSum(numbers,target);
   /*     for (int res:result) {
            System.out.println(res+"\t");
        }*/
        System.out.println(Arrays.toString(result));
    }
}