题目：

题解：

class Solution {
public:int nextGreaterElement(int n) {int x = n, cnt = 1;for (; x >= 10 && x / 10 % 10 >= x % 10; x /= 10) {++cnt;}x /= 10;if (x == 0) {return -1;}int targetDigit = x % 10;int x2 = n, cnt2 = 0;for (; x2 % 10 <= targetDigit; x2 /= 10) {++cnt2;}x += x2 % 10 - targetDigit; // 把 x2 % 10 换到 targetDigit 上for (int i = 0; i < cnt; ++i, n /= 10) { // 反转 n 末尾的 cnt 个数字拼到 x 后int d = i != cnt2 ? n % 10 : targetDigit;if (x > INT_MAX / 10 || x == INT_MAX / 10 && d > 7) {return -1;}x = x * 10 + d;}return x;}
};