Solution670.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;

/**
 * Created by slade on 2019/12/26.
 */
public class Solution670 {
 public int maximumSwap(int num) {
 ArrayList<Integer> arrayList = new ArrayList();
 while (num != 0) {
 arrayList.add(num % 10);
 num /= 10;
 }
 Collections.reverse(arrayList);
 ArrayList arrayList1 = new ArrayList(arrayList);
 arrayList1.sort(new Comparator() {
 @Override
 public int compare(Object o1, Object o2) {
 return (Integer) o1 > (Integer) o2 ? -1 : 1;
 }
 });
 for (int i = 0; i < arrayList.size(); i++) {
 if (arrayList.get(i) != arrayList1.get(i)) {
 int tmp = (int) arrayList1.get(i);
 int idx = arrayList.lastIndexOf(tmp);
 arrayList.set(idx, arrayList.get(i));
 arrayList.set(i, tmp);
 break;
 }
 }
 int res = 0;
 for (int i = 0; i < arrayList.size(); i++) {
 res = 10 * res + arrayList.get(i);
 }
 return res;
 }

 public static void main(String[] args) {
 Solution670 solution670 = new Solution670();
 System.out.println(solution670.maximumSwap(134120));
 }
}