注:大佬解答来自LetCode官方题解

80.删除有序数组的重复项Ⅱ

1.题目

 

 2.个人解答

var removeDuplicates = function (nums) {
  let res = [];

  for (let index = 0; index < nums.length; index++) {
    let num = 0;
    if (res.includes(nums[index])) {
      for (let i = 0; i < res.length; i++) {
        if (res[i] == nums[index]) {
          num++;
        }
      }
      if (num < 2) {
        res.push(nums[index]);
      }
      //得到num的次数
      if (num > 2) {
        return;
      }
    } else {
      res.push(nums[index]);
    }
  }


  nums.length=res.length

  for (let index = 0; index < res.length; index++) {
    nums[index]=res[index]
  }

};

3.大佬解答

var removeDuplicates = function(nums) {
    const n = nums.length;
    if (n <= 2) {
        return n;
    }
    let slow = 2, fast = 2;
    while (fast < n) {
        if (nums[slow - 2] != nums[fast]) {
            nums[slow] = nums[fast];
            ++slow;
        }
        ++fast;
    }
    return slow;
};

169.多数元素

1.题目

2.个人解答

var majorityElement = function (nums) {
  let result = 0;

  const res = Array.from(new Set([...nums]));
  res.forEach((item_nums) => {
    let n = nums.length / 2;
    nums.forEach((item_res) => {
      if (item_nums == item_res) {
        n = n - 1;
      }
    });

    if (n < 0) {
      result = item_nums;
    }
  });
  return result;
};

3.大佬解答

没解答

189.轮转数组

1.题目

2.个人解答

var rotate = function (nums, k) {
  for (let index = 0; index < k; index++) {
    nums.unshift(nums[nums.length - 1]);
    nums.pop();
  }
};

3.大佬解答

var rotate = function(nums, k) {
    const n = nums.length;
    const newArr = new Array(n);
    for (let i = 0; i < n; ++i) {
        newArr[(i + k) % n] = nums[i];
    }
    for (let i = 0; i < n; ++i) {
        nums[i] = newArr[i];
    }
};

const reverse = (nums, start, end) => {
    while (start < end) {
        const temp = nums[start];
        nums[start] = nums[end];
        nums[end] = temp;
        start += 1;
        end -= 1;
    }
}

var rotate = function(nums, k) {
    k %= nums.length;
    reverse(nums, 0, nums.length - 1);
    reverse(nums, 0, k - 1);
    reverse(nums, k, nums.length - 1);
};