leetcode 26. Remove Duplicates from Sorted Array

原地移除元素，返回新长度

const removeDuplicates = nums => {
    let index = 1;
    for (let i = 0; i < nums.length - 1; i++) {
        if (nums[i] != nums[i + 1]) {
            nums[index++] = nums[i + 1];
        }
    }
    nums.length = index
    return index;
};