556

Author: ProHiryu

Math/556.md

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+## 556 Next Greater Element III
+
+#### Description
+
+[link](https://leetcode.com/problems/next-greater-element-iii/)
+
+---
+
+#### Solution
+
+- 下一个排列问题，先从后往前找到第一个不是递减的数字，和后面第一个大于它的数字交换，如果没有变化或者过大，返回-1
+
+---
+
+#### Code
+
+<!-- O(n) -->
+
+```python
+class Solution:
+    def nextGreaterElement(self, n: int) -> int:
+        digits = list(str(n))
+        length = len(digits)
+        
+        i, j = length-2, length-1
+        while i >= 0 and digits[i+1] <= digits[i]:
+            i -= 1
+        
+        if i == -1: return -1
+
+        while digits[j] <= digits[i]:
+            j -= 1
+        
+        digits[i], digits[j] = digits[j], digits[i]
+
+        res = int(''.join(digits[:i+1] + digits[i+1:][::-1]))
+        if res >= 2**31 or res == n:
+            return -1
+        return res
+```