LeetCode - Largest Number
Problem description
Given a list of non negative integers, arrange them such that they form the largest number.
Example 1:
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Input: [10,2]
Output: "210"
Example 2:
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2
Input: [3,30,34,5,9]
Output: "9534330"
Note: The result may be very large, so you need to return a string instead of an integer.
Analysis
Basically, we can use a comparator to solve this. We test two order of combination for A and B, which is AB and BA. And we find out the bigger one(suppose it’s AB), which means A should always precedes B.
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class Solution {
private class LargerNumberComparator implements Comparator<String> {
@Override
public int compare(String a, String b) {
String order1 = a + b;
String order2 = b + a;
return order2.compareTo(order1);
}
}
public String largestNumber(int[] nums) {
// Get input integers as strings.
String[] asStrs = new String[nums.length];
for (int i = 0; i < nums.length; i++) {
asStrs[i] = String.valueOf(nums[i]);
}
// Sort strings according to custom comparator.
Arrays.sort(asStrs, new LargerNumberComparator());
// If, after being sorted, the largest number is `0`, the entire number
// is zero.
if (asStrs[0].equals("0")) {
return "0";
}
// Build largest number from sorted array.
String largestNumberStr = new String();
for (String numAsStr : asStrs) {
largestNumberStr += numAsStr;
}
return largestNumberStr;
}
}