398

Author: ProHiryu

RS/398.md

@@ -0,0 +1,39 @@
+## 398 Random Pick Index
+
+#### Description
+
+[link](https://leetcode.com/problems/random-pick-index/)
+
+---
+
+#### Solution
+
+- See Code
+
+---
+
+#### Code
+
+```python
+class Solution:
+
+    def __init__(self, nums: List[int]):
+        self.nums = collections.defaultdict(list)
+        for i, num in enumerate(nums):
+            self.nums[num].append(i)
+            
+
+    def pick(self, target: int) -> int:
+        lst = self.nums[target]
+        res = lst[0]
+        for i in range(1, len(lst)):
+            n = random.random()
+            if n < 1 / (1 + i):
+                res = lst[i]
+        return res
+
+
+# Your Solution object will be instantiated and called as such:
+# obj = Solution(nums)
+# param_1 = obj.pick(target)
+```