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// 2981. Find Longest Special Substring That Occurs Thrice I
#include "leetcode.h"
/*
* you are given a string 's' that consists of lowercase english letters. a
* string is called special if it is made up of only a single character. for
* example, the string 'abc' is not special, whereas the strongs 'ddd', 'zz',
* and 'f' are special. return the length of the longest special substring of
* 's' which occrs at least thrice, or -1 if no special substring occrs at least
* thrice. a substring is a contiguous non-empty sequence of characters within a
* string
*/
bool helper(char *s, int n, int x) {
int cnt[26] = {0}, c = 0;
for (int i = 0; i < n; i++) {
while (s[c] != s[i])
c++;
if (i - c + 1 >= x)
cnt[s[i] - 'a']++;
if (cnt[s[i] - 'a'] > 2)
return true;
}
return false;
}
int maximumLength(char *s) {
int n = strlen(s), l = 1, r = n;
if (!helper(s, n, l))
return -1;
while (l + 1 < r) {
int m = (l + r) / 2;
if (helper(s, n, m))
l = m;
else
r = m;
}
return l;
}
int main() {
char *s1 = "aaaa", *s2 = "abcdef", *s3 = "abcaba";
printf("%d\n", maximumLength(s1)); // expect: 2
printf("%d\n", maximumLength(s2)); // expect: -1
printf("%d\n", maximumLength(s3)); // expect: 1
}
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