answer of the same length as s with all elements set to a large number (e.g., s.length).prev to a large negative value to represent that we haven't seen the character c yet.s from left to right. For each index i, if s[i] is c, update prev to i. Then set answer[i] to i - prev.prev to a large positive value to represent that we haven't seen the character c from the right.s from right to left. For each index i, if s[i] is c, update prev to i. Then update answer[i] to the minimum of answer[i] and prev - i.answer array.