Update 0474.一和零.md

添加一和零 python3 版本

Author: haofengsiji

problems/0474.一和零.md

@@ -191,6 +191,31 @@ class Solution {
 
 Python：
 
+```python3
+class Solution:
+    def countBinary(self, s: str) -> (int, int):
+        zeros, ones = 0, 0
+        for c in s:
+            if c == '0':
+                zeros += 1
+            else:
+                ones += 1
+        return zeros, ones
+
+    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
+        dp = [[0]*(n + 1) for _ in range(m + 1)]	# 默认初始化0
+        # 遍历物品
+        for i in range(len(strs)): 
+            # num_zeros = strs[i].count('0')
+            # num_ones = strs[i].count('1')
+            num_zeros, num_ones = self.countBinary(strs[i])
+            # 遍历背包容量且从后向前遍历！
+            for j in range(m, num_zeros - 1, -1):
+                for i in range(n, num_ones - 1, -1):
+                    dp[j][i] = max(dp[j - num_zeros][i - num_ones] + 1, dp[j][i])
+        return dp[m][n]
+```
+
 
 Go：