Maximum Swap
Given a non-negative integer, you could swap two digits at most once to get the maximum valued number. Return the maximum valued number you could get.
Example
Example 1:
Input: 2736
Output: 7236
Explanation: Swap the number 2 and the number 7.
Example 2:
Input: 9973
Output: 9973
Explanation: No swap.
Note
本质是寻找右边第一个最大的和左边第一个比它小的。需要满足左右的位置关系
从右往左遍历,记录最大的值和位置,需要continue
遇到比最大小的就记录,一直往左会找到最左边比最大值小的那个数字
如果一直右往左一直递增,是特殊情况,第二个if语句不会执行,left会一直是-1,直接返回
Code
class Solution {
public int maximumSwap(int num) {
String s = String.valueOf(num);
char[] c = s.toCharArray();
int len = c.length;
int left = -1, right = -1;
int max = -1, index = -1;
for (int i = len - 1; i >= 0; i--) {
if (c[i] > max) {
index = i;
max = c[i];
continue;
}
if (c[i] < max) {
left = i;
right = index;
}
}
System.out.println(right + " " + left);
if (left == -1) {
return num;
}
char temp = c[left];
c[left] = c[right];
c[right] = temp;
return Integer.parseInt(String.valueOf(c));
}
}
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