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第一周

Algorithm

先从刷LeetCode开始吧！之前一直没刷过，坚持 刷 刷 刷

Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

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Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

刚开始使用暴力解法直接双重循环

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Public int[] twoSum(int[] nums, int target) {
    for (int i = 0; i < nums.length; i++) {
        for (int j = i + 1; j < nums.length; j++) {
            if (nums[j] == target - nums[i]) {
                return new int[] { i, j };
            }
        }
    }
    throw new IllegalArgumentException("No two sum solution");
}

写完之后看了下被人的解法
其中

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public int[] twoSum(int[] nums, int target) {
        Map<Integer,Integer> map = new HashMap<>();
        for(int i = 0;i < nums.length;i++){
            int v = target - nums[i];
            if(map.containsKey(v)){
                return new int[]{map.get(v),i};
            }
            map.put(nums[i],i);
        }
        throw new IllegalArgumentException("No two sum solution");
    }

这个是如果没有刷过自己是想不到的利用map的containsKey减少了一层循环然后去看了HashMap的这个的实现是调用了如下方法

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final Node<K,V> getNode(int hash, Object key) {
        Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
        if ((tab = table) != null && (n = tab.length) > 0 &&
            (first = tab[(n - 1) & hash]) != null) {
            if (first.hash == hash && // always check first node
                ((k = first.key) == key || (key != null && key.equals(k))))
                return first;
            if ((e = first.next) != null) {
                if (first instanceof TreeNode)
                    return ((TreeNode<K,V>)first).getTreeNode(hash, key);
                do {
                    if (e.hash == hash &&
                        ((k = e.key) == key || (key != null && key.equals(k))))
                        return e;
                } while ((e = e.next) != null);
            }
        }
        return null;
    }

这就是所谓的用空间换时间吧

Rewiew

Tip

在用apache搭建 webdav 时遇到文件名称中文乱码
在这里插入图片描述
看这里主要描述了IndexOptions配置的作用
在httpd.conf 加上 IndexOptions Charset=UTF-8 即可解决
在这里插入图片描述