670. Maximum Swap
Given a non-negative integer, you could swap two digits at most once to get the maximum valued number. Return the maximum valued number you could get.
Example 1:
Input: 2736 Output: 7236 Explanation: Swap the number 2 and the number 7.
Example 2:
Input: 9973 Output: 9973 Explanation: No swap.
Note:
- The given number is in the range [0, 108]
Approach #1: Math. [Java]
class Solution { public int maximumSwap(int num) { char[] digits = Integer.toString(num).toCharArray(); int[] buckets = new int[10]; for (int i = 0; i < digits.length; ++i) buckets[digits[i]-'0'] = i; for (int i = 0; i < digits.length; ++i) { for (int j = 9; j > digits[i]-'0'; --j) { if (buckets[j] > i) { char temp = digits[i]; digits[i] = digits[buckets[j]]; digits[buckets[j]] = temp; return Integer.valueOf(new String(digits)); } } } return num; } }
Analysis:
https://leetcode.com/problems/maximum-swap/discuss/107068/Java-simple-solution-O(n)-time
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