75. Sort Colors

Given an array 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.

Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.

Note: You are not suppose to use the library's sort function for this problem.

Example:

Input: [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Follow up:

• A rather straight forward solution is a two-pass algorithm using counting sort.
  First, iterate the array counting number of 0's, 1's, and 2's, then overwrite array with total number of 0's, then 1's and followed by 2's.
• Could you come up with a one-pass algorithm using only constant space?

 

my code:

class Solution {
public:
    void sortColors(vector<int>& nums) {
        int len = nums.size();
        for (int i = 1; i <= len; ++i) {
            for (int j = i-1; j > 0; --j) {
                if (nums[j] < nums[j-1]) {
                    int con = nums[j];
                    nums[j] = nums[j-1];
                    nums[j-1] = con;
                }
            }
        }
    }
};

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Sort Colors.