# Sort Colors

{% embed url="<https://leetcode.com/problems/sort-colors/>" %}

{% embed url="<https://www.lintcode.com/problem/148/>" %}

## Solution 1 (Go)

```go
func sortColors(nums []int)  {
    j := 0
    for i := 0; i < len(nums); i++ {
        if nums[i] == 0 {
            nums[i], nums[j] = nums[j], nums[i]
            j++
        }
    }
    
    for i := j; i < len(nums); i++ {
        if nums[i] == 1 {
            nums[i], nums[j] = nums[j], nums[i]
            j++
        }
    }
}
```

## Solution 2 (Go)

```go
func sortColors(nums []int)  {
    i, j, k := 0, 0, len(nums)-1
    for j <= k {
        if nums[j] == 0 {
            nums[i], nums[j] = nums[j], nums[i]
            i++
            j++
        } else if nums[j] == 1 {
            j++
        } else {
            nums[j], nums[k] = nums[k], nums[j]
            k--
        }
    }
}
```

`[0, i)`: the interval containing all 0's

`[i, j)`: the interval containing all 1's

`[j ,k)`: the interval to be explored

`[k ,len(nums))`: the interval containing all 2's

## Solution 3 (Java)

```java
public class Solution {
    /**
     * @param nums: A list of integer which is 0, 1 or 2 
     * @return: nothing
     */
    public void sortColors(int[] nums) {
        quickSort(nums, 1);
        quickSort(nums, 2);
    }

    private void quickSort(int[] nums, int k) {
        if (nums == null) return;
        int i = 0, j = nums.length - 1;
        while (i <= j) {
            while (i <= j && nums[i] < k) {
                i++;
            }
            while (i <= j && nums[j] >= k) {
                j--;
            }
            if (i <= j) {
                int temp = nums[i];
                nums[i] = nums[j];
                nums[j] = temp;
            }
        }
    }
}
```

### Notes

* **Quick sort**

## Solution 4 (Java)

```java
public class Solution {
    /**
     * @param nums: A list of integer which is 0, 1 or 2 
     * @return: nothing
     */
    public void sortColors(int[] nums) {
        Arrays.sort(nums);
    }
}
```

### Notes

* Not really a "solution"...

## Solution 5 (Java)

```java
public class Solution {
    /**
     * @param nums: A list of integer which is 0, 1 or 2 
     * @return: nothing
     */
    public void sortColors(int[] nums) {
        int i = 0, j = 0, k = nums.length - 1;
        while (j <= k) {
            if (nums[j] == 0) {
                swap(nums, j, i);
                i++;
                j++;
            } else if (nums[j] == 1) {
                j++;
            } else {
                swap(nums, j, k);
                k--;
            }
        }
    }

    private void swap(int[] nums, int a, int b) {
        int temp = nums[a];
        nums[a] = nums[b];
        nums[b] = temp;
    }
}

// [0, i) all 0's
// [i, j) all 1's
// [j, k) exploring
// [k, nums.length - 1) all 2's
```

### Notes

* Same as [Solution 2](/algo/sorting/sort-colors-1.md#solution-2-go) but in Java.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://blog.yushunchen.com/algo/sorting/sort-colors-1.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.