LeetCode Solutions
class Solution {
public:
int uniqueLetterString(string s) {
int ans = 0;
int count = 0;
vector<int> lastCount(26);
vector<int> lastSeen(26, -1);
for (int i = 0; i < s.length(); ++i) {
const int c = s[i] - 'A';
const int currentCount = i - lastSeen[c];
count = count - lastCount[c] + currentCount;
lastCount[c] = currentCount;
lastSeen[c] = i;
ans += count;
}
return ans;
}
};
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class Solution {
public int uniqueLetterString(String s) {
int ans = 0;
int count = 0;
int[] lastCount = new int[26];
int[] lastSeen = new int[26];
Arrays.fill(lastSeen, -1);
for (int i = 0; i < s.length(); ++i) {
final int c = s.charAt(i) - 'A';
final int currentCount = i - lastSeen[c];
count = count - lastCount[c] + currentCount;
lastCount[c] = currentCount;
lastSeen[c] = i;
ans += count;
}
return ans;
}
}
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class Solution:
def uniqueLetterString(self, s: str) -> int:
ans = 0
count = 0
lastCount = [0] * 26
lastSeen = [-1] * 26
for i, c in enumerate(s):
c = ord(c) - ord('A')
currentCount = i - lastSeen[c]
count = count - lastCount[c] + currentCount
lastCount[c] = currentCount
lastSeen[c] = i
ans += count
return ans
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