Largest Number

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 is9534330.

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

[分析]

按題目的要求, 重寫排序方法, 然後排序即可.

[注意]

當一個數是另一個數的字首時, 要注意順序. 這裡用了個小技巧   比較   S1+S2 ? S2+S1 即可.

另外, leading zeros要去掉.

[CODE]

second try:

public class Solution {
    public String largestNumber(int[] arr) {
        Integer[] array = new Integer[arr.length];
		int i = 0;
		for (int value : arr) {
		    array[i++] = Integer.valueOf(value);
		}		
		
		Arrays.sort(array, new Comparator<Integer>() {
			@Override
			public int compare(Integer a1, Integer a2) {
				int l1 = a1==0? 1 :  (int) Math.log10(Math.abs(a1)) + 1;
				int l2 = a2==0? 1 :  (int) Math.log10(Math.abs(a2)) + 1;
				
				long aa1 = (long) (a1 * Math.pow(10, l2) + a2);
				long aa2 = (long) (a2 * Math.pow(10, l1) + a1);
				
				return aa1>aa2 ? -1 : (aa1==aa2 ? 0 : 1);
			}
		}
				);
		StringBuilder sb = new StringBuilder();
		for(Integer e : array) {
			sb.append(e);
		}
		return sb.toString().replaceFirst("^0+(?!$)", "");
    }
}
 

first edition:

public class Solution {
    public String largestNumber(int[] arr) {
        String[] strs = new String[arr.length];
		
		for(int i=0; i<arr.length; i++) {
			strs[i] = Integer.toString(arr[i]);
		}
		
		Arrays.sort(strs, new Comparator<String>() {
			@Override
			public int compare(String s1, String s2) {
				String ss1 = s1 + s2;
				String ss2 = s2 + s1;
				int i=0;
				while(i<ss1.length()) {
					if(ss1.charAt(i)!=ss2.charAt(i)) {
						return ss1.charAt(i) - ss2.charAt(i);
					}
					++i;
				}
				return 0;
			}
		}
				);
		
		StringBuilder sb = new StringBuilder();
		for(int i=strs.length-1; i>=0; i--) {
		    sb.append(strs[i]);
		}
		
		return sb.toString().replaceFirst("^0+(?!$)", "");	
    }
}