LeetCode: Sort Colors

没写出来，看到网上一个非常好的code，不过这个code不太容易想出来

class Solution {
public:
    void sortColors(int A[], int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int pos[3] = {};
        for (int i = 0; i < n; i++) {
            int cur = A[i];
            for (int j = 2; j >= cur; j--) {
                A[pos[j]] = j;
                pos[j]++;
            }
        }
    }
};

下面是一个比较容易想出来的code。

class Solution {
public:
    void sortColors(int A[], int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int left = 0;
        int right = n-1;
        int mid = n-1;
        while (left <= mid) {
            if (A[left] == 2) {
                int tmp = A[right];
                A[right] = A[left];
                A[left] = tmp;
                right--;
                if (right < mid) mid = right;
            }
            if (A[left] == 1) {
                int tmp = A[mid];
                A[mid] = A[left];
                A[left] = tmp;
                mid--;
            }
            if (A[left] == 0) left++;
        }
    }
};

 C#

public class Solution {
    public void SortColors(int[] nums) {
        int left = 0, right = nums.Length - 1, mid = nums.Length - 1;
        while (left <= mid) {
            if (nums[left] == 2) {
                int tmp = nums[right];
                nums[right] = nums[left];
                nums[left] = tmp;
                right--;
                if (right < mid) mid = right;
            }
            if (nums[left] == 1) {
                int tmp = nums[mid];
                nums[mid] = nums[left];
                nums[left] = tmp;
                mid--;
            }
            if (nums[left] == 0) left++;
        }
    }
}