c[s.charAt(i)]++;

#1

c[s.charAt(i)]++; how this will add the value
c[‘a’]++ ; means??? c[‘a’]=c[‘a’]+1; ??? Can you explain?

#2

@pallavigoel1996 this will just have the count of character a being held in c incremented by one. so every ‘char’ that is encountered increments its c[‘char’] inc by 1 .