179. 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.

自定义比较器，比较的准则是两个int，a和b，a在前大还是b在前大。

刚开始想复杂了，比较准则还想着按位来，居然也A掉了，然而其中的原理仍然感觉似乎不是那么站得住脚？

public String largestNumber(int[] nums){StringBuilder sb=new StringBuilder();int len=nums.length;Integer[] arr=new Integer[len];for(int i=0;i<len;i++)arr[i]=Integer.valueOf(nums[i]);Arrays.sort(arr, new mycomparator2());for(int i=len-1;i>=0;i--)sb.append(arr[i]);return new java.math.BigInteger(sb.toString()).toString();}

class mycomparator2 implements Comparator<Object>{public int compare(Object o1, Object o2){Integer io1=(Integer) o1;Integer io2=(Integer) o2;/*String s1=io1.toString();String s2=io2.toString();long cmp=Long.parseLong(s1+s2)-Long.parseLong(s2+s1);if(cmp>0)return 1;else if(cmp<0)return -1;return 0;*/if(io1==2&&io2==2281){System.out.println();}if(io1==0&&io2>0)return -1;else if(io1!=0&&io2==0)return 1;else if(io1==0&&io2==0)return 0;int cnt1=0;int cnt2=0;int[] bit1=new int[10];int[] bit2=new int[10];while(io1>0){bit1[cnt1++]=io1%10;io1/=10;}while(io2>0){bit2[cnt2++]=io2%10;io2/=10;}cnt1--;cnt2--;int cnt1cpy=cnt1;int cnt2cpy=cnt2;while(cnt1>=0&&cnt2>=0){if(bit1[cnt1]>bit2[cnt2])return 1;else if(bit1[cnt1]<bit2[cnt2])return -1;else {cnt1--;cnt2--;}}if(cnt1!=cnt2){if(cnt1<0){while(cnt2>=0){cnt1=cnt1cpy;while(cnt1>=0){if(bit2[cnt2]<bit1[cnt1])return 1;else if(bit2[cnt2]>bit1[cnt1])return -1;cnt1--;}cnt2--;}}else if(cnt2<0){while(cnt1>=0){cnt2=cnt2cpy;while(cnt2>=0){if(bit1[cnt1]>bit2[cnt2])return 1;else if(bit1[cnt1]<bit2[cnt2])return -1;cnt2--;}cnt1--;}}}return 0;}}

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public class Solution {    public String largestNumber(int[] nums){int len=nums.length;quick_sort(nums,0,len-1);StringBuilder sb=new StringBuilder();for(int i=len-1;i>=0;i--)sb.append(nums[i]);if(sb.length()>0&&sb.charAt(0)=='0')    return "0";    return sb.toString();}public int compare(int o1, int o2){String s1=String.valueOf(o1);String s2=String.valueOf(o2);long cmp=Long.parseLong(s1+s2)-Long.parseLong(s2+s1);if(cmp>0)return 1;else if(cmp<0)return -1;return 0;}private int partition(int[] a,int lo ,int hi){int i=lo;int j=hi+1;int v=a[lo];while(true){while(compare(a[++i], v)<0) if(i==hi)break;while(compare(v, a[--j])<0)if(j==lo)break;if(i>=j)break;swap(a, i, j);}swap(a, lo, j);return j;}public void quick_sort(int[] a,int lo,int hi){if(hi<=lo)return ;int j=partition(a, lo, hi);quick_sort(a, lo, j-1);quick_sort(a, j+1, hi);}public  void swap(int[] a,int i,int j){int temp=a[i];a[i]=a[j];a[j]=temp;}}