leetcode-139-word-break.swift

/**

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OR OTHER DEALINGS IN THE SOFTWARE.





https://leetcode.com/problems/word-break/


Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

Note:

The same word in the dictionary may be reused multiple times in the segmentation.
You may assume the dictionary does not contain duplicate words.
Example 1:

Input: s = "leetcode", wordDict = ["leet", "code"]
Output: true
Explanation: Return true because "leetcode" can be segmented as "leet code".
Example 2:

Input: s = "applepenapple", wordDict = ["apple", "pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
             Note that you are allowed to reuse a dictionary word.
Example 3:

Input: s = "catsandog", wordDict = ["cats", "dog", "sand", "and", "cat"]
Output: false

*/

/**
Big O Annotation
Time complexity O(n) where n is the amount of elements in nums.
Space complexity O(n) where n is the amount of elements in nums.
*/
func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
        
    // Get mutable copy of the string
    var s = s

    // Iterate through the list of words
    for element in wordDict {

        /**
        Try replacing the string's occurence 
        of element with an empty ""
        */
        let replaced = s.replacingOccurrences(of: element, with: "")
    
        // If we have't replaced anything, return false
        if replaced == s {
            return false 
        }

        // Otherwise set string to the new one
        s = replaced
    }
    
    // The function succeeds if s is now empty.
    return s.isEmpty
}