1540. Can Convert String in K Moves

Given two strings s and t, your goal is to convert s into t in k moves or less.

During the ith (1 <= i <= k) move you can:

• Choose any index j (1-indexed) from s, such that 1 <= j <= s.length and j has not been chosen in any previous move, and shift the character at that index i times.
• Do nothing.

Shifting a character means replacing it by the next letter in the alphabet (wrapping around so that ‘z’ becomes ‘a’). Shifting a character by i means applying the shift operations i times.

Remember that any index j can be picked at most once.

Return true if it’s possible to convert s into t in no more than k moves, otherwise return false.

class Solution {
public:
    bool canConvertString(string s, string t, int k) {
        if(s.length() != t.length())
            return false;
        unordered_map<int, int> m;
        for(int i = 0; i < s.length(); i++) {
            m[(t[i] - s[i] + 26) % 26]++;
        }
        
        for(int i = 1; i < 26; i++) {
            if(m[i] && (m[i] - 1)*26 + i > k)
                return false;
        }
        return true;
    }
};

class Solution {
public:
    bool canConvertString(string s, string t, int k) {
        if(s.length() != t.length())
            return false;
        unordered_map<int, int> m;
        int diff = -1;
        for(int i = 0; i < s.length() && m[diff] <= k; i++) {
            diff = (t[i] - s[i] + 26) % 26;
            m[diff] += m[diff] ? 26 : diff;
        }
        return m[diff] <= k;
    }
};