026_Remove_Duplicates_from_Sorted_Array.md

26. Remove Duplicates from Sorted Array

---

Description

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

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

For example, Given input array nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn't matter what you leave beyond the new length.

Javascript

思路：hash判断是否重复，然后使用splice方法。

/**
 * @param {number[]} nums
 * @return {number}
 */
var removeDuplicates = function(nums) {
    var dic = {};
    for (var i = 0; i < nums.length; i++) {
        if (dic[nums[i]] === undefined) {
            dic[nums[i]] = 1;
        } else {
            nums.splice(i, 1);
            i--;
        }
    }
    return nums.length;
};

Java

解法： 双指针，一个指向已经去重的位置，一个指向下一个该出现的元素。

public class Solution {
    public int removeDuplicates(int[] nums) {
        if (nums.length <= 1) return nums.length;
        int i = 1, j = 1;
        while (i < nums.length && j < nums.length) {
            if (nums[i] <= nums[i - 1]) {
                while (j < nums.length && nums[j] <= nums[i - 1]) j++;
                if (j == nums.length) break;
                nums[i] = nums[j];
                i++;
                j++;
            } else {
                i++;
            }
        }
        return i;
    }
}

解法二：（这个更简单）

public class Solution {
    public int removeDuplicates(int A[], int n) {
        if(n < 2) return n;
        int id = 1;
        for(int i = 1; i < n; ++i) 
            if(A[i] != A[i-1]) A[id++] = A[i];
        return id;
    }
};