Go Leetcode: Crop N Length String

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Problem

Given a string s, return a cropped which max length is n.
Also, spaces at prefix and postfix need to be removed.

Example 1:

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Input: "Hello World", 8
Output: "Hello"

Example 2:

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Input: "   Hello World   ", 100
Output: "Hello World"

Example 3:

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Input: "Hello World", 3
Output: ""

Thought

Find the start point l and end point r then return result s[l:r]
Left point is easy to find. If s[l] is space, pointer l move right.
On the other hand, r starts from l + N, if s[r] is NOT space, pointer r move left.

The tricky point is that if the given string’s length equals to given n,
and the string ends with character, the last word would be cropped.

Example:

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Input: "Learn Golang", 12
Output: "Learn"
Expected: "Learn Golang"

An easy solution is to append a SPACE to the given string at the beginning.

Code

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func crop(s string, n int) string {
	s = s + " " // append an extra space

    // keep moving right until reaching the first character
	l := 0
	for l < len(s)-1 {
		if s[l] == ' ' {
			l++
		} else {
			break
		}
	}

    // start from `l+n` or the last char (extra space)
    // keep moving left until reaching the first space
	r := min(l+n, len(s)-1)
	for r > l {
		if s[r] == ' ' {
			break
		} else {
			r--
		}
	}
	return s[l:r]
}

func min(i, j int) int {
	if i < j {
		return i
	}
	return j
}