Leetcode题解14 27. Remove Element

最新推荐文章于 2022-07-03 00:53:38 发布

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本文介绍了一种在原地移除数组中特定值并返回新长度的算法实现。使用HashMap来存储非目标值及其出现次数，确保常数空间复杂度的同时，改变了原有元素的顺序。

Given an array and a value, remove all instances of that value in place and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

The order of elements can be changed. It doesn’t matter what you leave beyond the new length.

Example:
Given input array nums = [3,2,2,3], val = 3

Your function should return length = 2, with the first two elements of nums being 2.

用hashmap存储数组中值不是val的所有元素，键为元素值，值为元素出现次数。轻松搞定。

 public static int removeElement(int[] nums, int val) {
        HashMap<Integer, Integer> hashMap = new HashMap<Integer, Integer>();
        int count = 0;
        int temp;
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != val) {
                if (hashMap.get(nums[i]) != null) {
                    temp = hashMap.get(nums[i]);
                    hashMap.put(nums[i], ++temp);
                } else {
                    hashMap.put(nums[i], 1);
                }
            }
        }
        Iterator it = hashMap.keySet().iterator();
        while (it.hasNext()) {
            int key = (int) it.next();
            for (int i = 0; i < hashMap.get(key); i++) {
                nums[count] = key;
                count++;
            }
        }
        return count;
    }