2260. Minimum Consecutive Cards to Pick Up

You are given an integer array cards where cards[i] represents the value of the ith card. A pair of cards are matching if the cards have the same value.

Return the minimum number of consecutive cards you have to pick up to have a pair of matching cards among the picked cards. If it is impossible to have matching cards, return -1.

class Solution {
public:
    int minimumCardPickup(vector<int>& c) {
        unordered_map<int, vector<int>> mp;
        int n = c.size(), res = INT_MAX;
        for(int i = 0; i < n; i++) {
            mp[c[i]].push_back(i);
        }
        for(auto& [_, v] : mp) {
            for(int i = 0; i < v.size() - 1; i++) {
                res = min(res, v[i + 1] - v[i] + 1);
            }
        }
        return res == INT_MAX ? -1 : res;
    }
};