给定一个数组和一个目标整数

private static int []  m(int[] arr , int target){
        Map<Integer,Integer> map = new HashMap<>(arr.length);
        int [] result = new int[2];
        for(int i=0;i<arr.length;i++){
            int v = arr[i];
            if( map.containsKey(target-v)){
                result[0] = map.get(target-v);
                result[1] = i;
                break;
            }
            map.put(v,i);
        }
        return result;
    }

利用map；key=值，value = 下标 快速查找

https://blog.csdn.net/qq_42553504/article/details/115400048