LeetCode Hot 100 P75 Sort Colors

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Timeline

Timeline

2026-03-17

init

Two pointers

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Problem:

P75 Sort Colors

https://leetcode.cn/problems/sort-colors/description/?envType=study-plan-v2&envId=top-100-liked

Two pointers

#include <vector>
using std::vector;

class Solution {
    public:
        void sortColors(vector<int> &nums)
        {
                // n == nums.length
                // 1 <= n <= 300
                // nums[i] is 0, 1, or 2
                int n = nums.size();
                int red = 0, blue = n - 1;
                int i = 1;

                while (red < blue && i <= blue) {
                        if (nums[i] == 0) {
                                if (i != red)
                                        std::swap(nums[i], nums[red]);
                                else
                                        i++;

                                red++;
                        } else if (nums[i] == 2) {
                                if (i != blue)
                                        std::swap(nums[i], nums[blue]);
                                else
                                        i++;

                                blue--;
                        } else {
                                i++;
                        }
                }
        }
};

int main()
{
        vector<int> nums = { 2, 0, 2, 1, 1, 0 };
        Solution S;
        S.sortColors(nums);
}