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This approach uses a greedy method to partition the string. We traverse the string while keeping track of seen characters in a HashSet. When a repeating character is encountered, we start a new substring. This way, we ensure that each substring contains unique characters.
Time Complexity: O(n), where n is the length of the string, as we traverse each character once.
Space Complexity: O(1), since the size of the HashSet or boolean array is constant (fixed alphabet size).
1function minSubstrings(s) {
2 const seen = new Set();
3 let count = 0;
4
5 for (const char of s) {
6 if (seen.has(char)) {
7 count++;
8 seen.clear();
9 }
10 seen.add(char);
11 }
12 return count + 1;
13}
14
15console.log(minSubstrings("abacaba")); // Output: 4A Set allows tracking of seen characters in the current substring, initiating a new substring when repetition occurs.
With the two-pointer technique, one pointer iterates over the string while another pointer marks the start of a current substring. If a repeat character is found, we adjust the start pointer to ensure all characters between the start and end pointers remain unique.
Time Complexity: O(n), bounds on string traversal.
Space Complexity: O(1), with 26 possible character slots.
1
A lastSeen array helps track character indices, using it to determine new starting points for substrings when duplicates are encountered.