> For the complete documentation index, see [llms.txt](https://lei-d.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lei-d.gitbook.io/leetcode/string/709to-lower-case.md).

# 709\_To Lower Case

\[easy] \[string]

Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase.

**Example 1:**

```
Input: "Hello"
Output: "hello"
```

## Solution:

**Idea**:

* The ASCII code for lowercase and uppercase is different by 32.

**Time Complexity**: $$O(n)$$

**Space Complexity**: $$O(n)$$

```python
def toLowerCase(str):
    """
    :type str: str
    :rtype: str
    """

    # use build-in function in python
    # return str.lower()

    # use ASCII code
    out = ''
    for c in str:
        if ord(c) <= 90 and ord(c) >= 65:
            c = chr(ord(c) + 32)
        out += c
    return out
```


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