A Special Keyboard

Imagine you have a special keyboard with all keys in a single row. The layout of characters on a keyboard is denoted by a string S1 of length 26. S1 is indexed from 0 to 25. Initially, your finger is at index 0.

To type a character, you have to move your finger to the index of the desired character. The time taken to move your finger from index i to index j is |j-i|, where || denotes absolute value.Find the time taken to type the string S2 with the given keyboard layout.

• Time : O(n)
• Space : O(1)

class Solution {
public:
    int findTime(string S1, string S2) {
        unordered_map<char, int> mp;
        for(int i = 0; i < 26; i++) mp[S1[i]] = i;
        int res = 0;
        char prv = S1[0];
        for(auto& ch : S2) {
            res += abs(mp[ch] - mp[prv]);
            prv = ch;
        }
        return res;
    }
};