feat: 560.subarray-sum-equals-k add Python3 implementation (#150)

Author: ybian19

problems/560.subarray-sum-equals-k.md

@@ -1,5 +1,3 @@
-
-
 ## 题目地址
 https://leetcode.com/problems/subarray-sum-equals-k/description/
 
@@ -38,6 +36,11 @@ The range of numbers in the array is [-1000, 1000] and the range of the integer
 - 可以利用hashmap记录和的累加值来避免重复计算
 
 ## 代码
+
+* 语言支持：JS, Python
+
+Javascript Code:
+
 ```js
 /*
  * @lc app=leetcode id=560 lang=javascript
@@ -53,7 +56,7 @@ var subarraySum = function(nums, k) {
   const hashmap = {};
   let acc = 0;
   let count = 0;
-  
+
   for (let i = 0; i < nums.length; i++) {
     acc += nums[i];
 
@@ -74,10 +77,26 @@ var subarraySum = function(nums, k) {
 };
 ```
 
+Python Code:
+
+```python
+class Solution:
+    def subarraySum(self, nums: List[int], k: int) -> int:
+        d = {}
+        acc = count = 0
+        for num in nums:
+            acc += num
+            if acc == k:
+                count += 1
+            if acc - k in d:
+                count += d[acc-k]
+            if acc in d:
+                d[acc] += 1
+            else:
+                d[acc] = 1
+        return count
+```
+
 ## 扩展
 
 这是一道类似的题目，但是会稍微复杂一点, 题目地址: [437.path-sum-iii](./437.path-sum-iii.md)
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