167. Two Sum II

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.

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int m = 0, n = numbers.length - 1;
        while(m < n){
            if(numbers[m] + numbers[n] == target) return new int[] {m+1, n+1};
            else if(numbers[m] + numbers[n] > target) n--;
            else m++;
        }
        return new int[] {0,0};
    }
}

1.查找

class Solution {
    public int[] twoSum(int[] nums, int target){
        Map<Integer, Integer> map = new HashMap<>();
        for(int i = 0; i < nums.length; i++){
            int com = target - nums[i];
            if(map.containsKey(com) && map.get(com) != i){
                return new int[] {map.get(com) + 1, i + 1};
            }
            map.put(nums[i],i);
        }
        return new int[] {0,0};
    }
}

2.老方法