167.两数之和 II - 输入有序数组 - 双指针+哈希数组

原题链接：https://leetcode.cn/problems/two-sum-ii-input-array-is-sorted/

题解

方法1：双指针
左指针和右指针从数组两边开始遍历
当和小于target时左指针++，反之右指针–

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int leftItr=0,rightItr= numbers.length-1;
        while (leftItr!=rightItr){
            if(numbers[leftItr]+numbers[rightItr]==target){
                break;
            }else if(numbers[leftItr]+numbers[rightItr]>target){
                rightItr--;
            }else{
                leftItr++;
            }
        }
        int[]ans= {leftItr+1,rightItr+1};
        return ans;
    }
}

方法2：哈希数组

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int[] map=new int[3001];
        int i;
        for(i=0;i<numbers.length;i++){
            if(map[target-numbers[i]+1000]!=0){
                break;
            }
            if(map[numbers[i]+1000]==0){
                map[numbers[i]+1000]=i+1;
            }
        }
        int[] ans={map[target-numbers[i]+1000],i+1};
        return ans;
    }
}