【Leetcode】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 is

9534330

.

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

这道题还是有一定难度的，关键在于你要对数字怎么排序，后来我想到一个好办法：

比如85和859谁放在前面后呢？

让85859和85985比一下，也就是说

compare(int a,int b){

return Long.parseLong(a+""+b)- Long.parseLong(a+""+b);

}

所以其他的就简单啦~

package testAndfun;

import java.util.Arrays;
import java.util.Comparator;

public class largestNumber {
public static void main(String[] args) {
largestNumber ln = new largestNumber();
int[] in = { 3, 2, 54, 9, 85, 859, 99 };
//		sortNum(in);
System.out.println(ln.biggestNumber(in));
}

// 按自定义规则排序
public static void sortNum(int[] a) {
int temp = 0;
for (int i = a.length - 1; i > 0; --i) {
for (int j = 0; j < i; ++j) {
if (compare(a[j+1],a[j])<0) {
temp = a[j];
a[j] = a[j + 1];
a[j + 1] = temp;
}
}
}
}

// 输出
public String biggestNumber(int[] num) {
String output = new String();
sortNum(num);
for (int i = num.length-1; i >= 0; i--) {
output += num[i] + "";
}
if(output.length()>1 && output.charAt(0)=='0')	return 0+"";
return output;
}

// 排序规则
public static int compare(int o1, int o2) {
String s1 = o1 + "" + o2;
String s2 = o2 + "" + o1;
return (int) (Long.parseLong(s1) - Long.parseLong(s2));
}
}