g1901_2000.s1946_largest_number_after_mutating_substring.Solution Maven / Gradle / Ivy

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package g1901_2000.s1946_largest_number_after_mutating_substring;

// #Medium #Array #String #Greedy #2022_05_18_Time_18_ms_(70.91%)_Space_72.8_MB_(9.09%)

/**
 * 1946 - Largest Number After Mutating Substring\.
 *
 * Medium
 *
 * You are given a string `num`, which represents a large integer. You are also given a **0-indexed** integer array `change` of length `10` that maps each digit `0-9` to another digit. More formally, digit `d` maps to digit `change[d]`.
 *
 * You may **choose** to **mutate a single substring** of `num`. To mutate a substring, replace each digit `num[i]` with the digit it maps to in `change` (i.e. replace `num[i]` with `change[num[i]]`).
 *
 * Return _a string representing the **largest** possible integer after **mutating** (or choosing not to) a **single substring** of_ `num`.
 *
 * A **substring** is a contiguous sequence of characters within the string.
 *
 * **Example 1:**
 *
 * **Input:** num = "132", change = [9,8,5,0,3,6,4,2,6,8]
 *
 * **Output:** "832"
 *
 * **Explanation:** Replace the substring "1": 
 *
 * - 1 maps to change[1] = 8. Thus, "132" becomes "832". 
 *   
 * "832" is the largest number that can be created, so return it.
 *
 * **Example 2:**
 *
 * **Input:** num = "021", change = [9,4,3,5,7,2,1,9,0,6]
 *
 * **Output:** "934"
 *
 * **Explanation:** Replace the substring "021": 
 *
 * - 0 maps to change[0] = 9. 
 *
 * - 2 maps to change[2] = 3. 
 *
 * - 1 maps to change[1] = 4. 
 *   
 * Thus, "021" becomes "934". 
 *
 * "934" is the largest number that can be created, so return it.
 *
 * **Example 3:**
 *
 * **Input:** num = "5", change = [1,4,7,5,3,2,5,6,9,4]
 *
 * **Output:** "5"
 *
 * **Explanation:** "5" is already the largest number that can be created, so return it.
 *
 * **Constraints:**
 *
 * *   1 <= num.length <= 10⁵
 * *   `num` consists of only digits `0-9`.
 * *   `change.length == 10`
 * *   `0 <= change[d] <= 9`
**/
public class Solution {
    public String maximumNumber(String num, int[] change) {
        int n = num.length();
        char[] nums = num.toCharArray();
        char[] arr = new char[n];
        for (int i = 0; i < n; i++) {
            int val = nums[i] - '0';
            arr[i] = (char) (change[val] + '0');
        }
        boolean flag = false;
        for (int i = 0; i < n; i++) {
            if (nums[i] < arr[i]) {
                nums[i] = arr[i];
                flag = true;
            } else if (flag && nums[i] > arr[i]) {
                break;
            }
        }
        return String.valueOf(nums);
    }
}