_1358.java

packagecom.fishercoder.solutions.secondthousand;

publicclass_1358 {
publicstaticclassSolution1 {
/*
 * A classic sliding window problem, no dp or backtracking, just sliding window: use two pointers.
 * my new favorite question!
 */
publicintnumberOfSubstrings(Strings) {
int[] counts = newint[3];
inti = 0;
intn = s.length();
intresult = 0;
for (intj = 0; j < n; j++) {
counts[s.charAt(j) - 'a']++;
while (counts[0] > 0 && counts[1] > 0 && counts[2] > 0) {
counts[s.charAt(i++) - 'a']--;
 }
result += i;
 }
returnresult;
 }
 }
}