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[LeetCode 179] Largest Number

Question

link

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

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Analysis

Please refer to [[ItInt5] Numbers Concatenation Max (Largest Number)(/blog/2014/08/17/Numbers-Concatenation-Max/).

Solution

Note that we can not override Comparator(Integer). So we must first convert int to string then sort.

Code

public class Solution {

    // this code should pass
    public String largestNumber(int[] num) {
        if (num == null || num.length == 0) {
            return "0";
        }
        String[] strs = new String[num.length];
        for (int i = 0; i < num.length; i++) {
            strs[i] = String.valueOf(num[i]);
        }
        Arrays.sort(strs, new LargerComparator());

        String res = "";
        for (String str : strs) {
            res = res + str;
        }
        return res;
    }

    class LargerComparator implements Comparator<String> {

        public int compare(String a, String b) {
            String first = a + b;
            String second = b + a;
            return second.compareTo(first);
        }
    }
}