week2 75. Sort Colors

public class Solution {
    public void sortColors(int[] nums) {
        if(nums == null || nums.length == 0){
            return;
        }
        
        int len = nums.length;
        int zero = 0;
        int one = 0;
        int two = 0;
        
        for(int i = 0; i < len; i++ ){
            if(nums[i]==0){
                zero++;
            }else if(nums[i]==1){
                one++;
            }else if(nums[i]==2){
                two++;
            }
}
    for (int i = 0; i < zero; i++){
        nums [i] = 0;
    }
    for (int i = zero; i < zero + one; i++){
        nums [i] = 1;
    }
    for (int i = zero + one; i < len; i++){
        nums [i] = 2;
    }
    return;
}
}