算法-二分查找-两个数之和

方法一 双指针

class Solution {
    
    
    public int[] twoSum(int[] numbers, int target) {
    
    
        if(numbers == null || numbers.length == 0) {
    
    
            return null;
        }
        int l = 0;
        int r = numbers.length - 1;
        int[] num = new int[2];
        while(l < r) {
    
    
            if(numbers[l] + numbers[r] == target) {
    
    
                num[0] = l + 1;
                num[1] = r + 1;
                return num;
                //return new int[] {l + 1, r + 1};   也可以直接这样返回
            }
            if(numbers[l] + numbers[r] > target) {
    
    
                r--;
            }else {
    
    
                l++;
            }
        }
        return null;
    }
}

方法而二 二分查找

class Solution {
    
    
    public int[] twoSum(int[] numbers, int target) {
    
    
        for (int i = 0; i < numbers.length; ++i) {
    
    
        //从当前数的后一个数开始找起
            int low = i + 1, high = numbers.length - 1;
            while (low <= high) {
    
    
                int mid = (high - low) / 2 + low;
                if (numbers[mid] == target - numbers[i]) {
    
    
                    return new int[]{
    
    i + 1, mid + 1};
                } else if (numbers[mid] > target - numbers[i]) {
    
    
                //你要找的值小于中间的值
                    high = mid - 1;
                } else {
    
    
                    low = mid + 1;
                }
            }
        }
        return new int[]{
    
    -1, -1};
    }
}