update

Author: jasoncao11

P103. 外观数列.md

@@ -0,0 +1,26 @@
+![algo42](./images/algo42.jpg)
+
+```
+class Solution:
+    def countAndSay(self, n: int) -> str:
+        pre = '1'
+        for i in range(n-1):
+            stack = []
+            count = ''
+            cur = ''
+            for ind, digit in enumerate(pre):
+                if stack and digit == stack[-1][1]:
+                    continue
+                if stack and digit != stack[-1][1]:
+                    last_ind, last_digit = stack.pop()
+                    count = str(ind-last_ind)
+                    cur += (count+str(last_digit))
+                stack.append([ind, digit])
+
+            last_ind, last_digit = stack.pop()
+            count = str(ind-last_ind+1)
+            cur += (count+str(last_digit)) 
+
+            pre = cur
+        return pre
+```