_1409.java

package com.fishercoder.solutions;

import java.util.HashMap;
import java.util.Map;

/**
 * 1409. Queries on a Permutation With Key
 *
 * Given the array queries of positive integers between 1 and m, you have to process all queries[i] (from i=0 to i=queries.length-1) according to the following rules:
 * In the beginning, you have the permutation P=[1,2,3,...,m].
 * For the current i, find the position of queries[i] in the permutation P (indexing from 0) and then move this at the beginning of the permutation P.
 * Notice that the position of queries[i] in P is the result for queries[i].
 * Return an array containing the result for the given queries.
 *
 * Example 1:
 * Input: queries = [3,1,2,1], m = 5
 * Output: [2,1,2,1]
 * Explanation: The queries are processed as follow:
 * For i=0: queries[i]=3, P=[1,2,3,4,5], position of 3 in P is 2, then we move 3 to the beginning of P resulting in P=[3,1,2,4,5].
 * For i=1: queries[i]=1, P=[3,1,2,4,5], position of 1 in P is 1, then we move 1 to the beginning of P resulting in P=[1,3,2,4,5].
 * For i=2: queries[i]=2, P=[1,3,2,4,5], position of 2 in P is 2, then we move 2 to the beginning of P resulting in P=[2,1,3,4,5].
 * For i=3: queries[i]=1, P=[2,1,3,4,5], position of 1 in P is 1, then we move 1 to the beginning of P resulting in P=[1,2,3,4,5].
 * Therefore, the array containing the result is [2,1,2,1].
 *
 * Example 2:
 * Input: queries = [4,1,2,2], m = 4
 * Output: [3,1,2,0]
 *
 * Example 3:
 * Input: queries = [7,5,5,8,3], m = 8
 * Output: [6,5,0,7,5]
 *
 * Constraints:
 * 1 <= m <= 10^3
 * 1 <= queries.length <= m
 * 1 <= queries[i] <= m
 * */
public class _1409 {
    public static class Solution1 {
        public int[] processQueries(int[] queries, int m) {
            Map<Integer, Integer> indexToValMap = new HashMap<>();
            for (int i = 1; i <= m; i++) {
                indexToValMap.put(i - 1, i);
            }
            int[] result = new int[queries.length];
            for (int i = 0; i < queries.length; i++) {
                int val = queries[i];
                int pos = findPos(indexToValMap, val);
                result[i] = pos;
                for (int j = pos; j > 0; j--) {
                    indexToValMap.put(j, indexToValMap.get(j - 1));
                }
                indexToValMap.put(0, val);
            }
            return result;
        }

        private int findPos(Map<Integer, Integer> map, int val) {
            for (int pos : map.keySet()) {
                if (map.get(pos) == val) {
                    return pos;
                }
            }
            return -1;
        }
    }
}