167. Two Sum II - Input array is sorted
Category: /leetcodeGiven an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.
We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.
You must solve this problem without using the library’s sort function.
Example 1:
Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]
Example 2:
Input: nums = [2,0,1]
Output: [0,1,2]
Example 3:
Input: nums = [0]
Output: [0]
Example 4:
Input: nums = [1]
Output: [1]
Constraints:
n == nums.length
1 <= n <= 300
nums[i] is 0, 1, or 2.
Follow up: Could you come up with a one-pass algorithm using only constant extra space?
Solution
def sortColors(self, nums):
l = curr = 0
r = len(nums) - 1
while curr <= r:
if nums[curr] == 0:
nums[l], nums[curr] = nums[curr], nums[l]
l += 1
curr += 1
elif nums[curr] == 2:
nums[r], nums[curr] = nums[curr], nums[r]
r -= 1
# note: no curr += 1, may be `2` again
else:
curr += 1
