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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int helper(char *s, int k) {
int n = strlen(s), type = 0, left = 0, right = 0, res = 0;
int *cn = calloc(3, sizeof(int));
for (int right = 0; right < n; right++) {
cn[s[right] - 'a']++;
if (cn[s[right] - 'a'] == 1)
type++;
while (type > k) {
cn[s[left] - 'a']--;
if (!cn[s[left] - 'a'])
type--;
left++;
}
res += right - left + 1;
}
return res;
}
int numberOfSubstrings(char *s) { return helper(s, 3) - helper(s, 2); }
int main() {
char s1[] = {"abcabc"}, s2[] = {"aaacb"}, s3[] = {"abc"};
printf("%d\n", numberOfSubstrings(s1)); // expect: 10
printf("%d\n", numberOfSubstrings(s2)); // expect: 3
printf("%d\n", numberOfSubstrings(s3)); // expect: 1
}
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