📝 docs : add 303. 区域和检索-数组不可变.md

Author: GoogTech

docs/LeetCode刷题之旅及题目解析/303.区域和检索-数组不可变/303.区域和检索-数组不可变.md

@@ -0,0 +1,80 @@
+## 303. 区域和检索 - 数组不可变
+> https://leetcode-cn.com/problems/range-sum-query-immutable/
+
+
+### Java
+```java
+/*
+ * @Author: Goog Tech
+ * @Date: 2020-09-15 15:07:30
+ * @LastEditTime: 2020-09-15 15:11:43
+ * @Description: https://leetcode-cn.com/problems/range-sum-query-immutable/
+ * @FilePath: \leetcode-googtech\#303. Range Sum Query - Immutable\Solution.java
+ * @Reference: https://leetcode-cn.com/problems/range-sum-query-immutable/solution/marveljian-dan-de-xue-xi-bi-ji-303-by-tyanyonecanc/
+ * @WebSite: https://algorithm.show/
+ */
+
+class NumArray {
+
+    private int[] sum;
+
+    // DP : 动态规划
+    public NumArray(int[] nums) {
+        sum = Arrays.copyOf(nums, nums.length);
+        for(int i = 1; i < sum.length; i++) {
+            // sum[i] 的值为 sum[0] 到 sum[i] 的所有值之和
+            sum[i] += sum[i - 1];
+        }
+    }
+    
+    public int sumRange(int i, int j) {
+        return (i == 0) ? sum[j] : (sum[j] - sum[i - 1]);
+    }
+}
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * NumArray obj = new NumArray(nums);
+ * int param_1 = obj.sumRange(i,j);
+ */
+```
+
+### Python
+```python
+'''
+Author: Goog Tech
+Date: 2020-09-15 15:07:34
+LastEditTime: 2020-09-15 15:08:56
+Description: https://leetcode-cn.com/problems/range-sum-query-immutable/
+FilePath: \leetcode-googtech\#303. Range Sum Query - Immutable\Solution.py
+Reference: https://leetcode-cn.com/problems/range-sum-query-immutable/solution/marveljian-dan-de-xue-xi-bi-ji-303-by-tyanyonecanc/
+WebSite: https://algorithm.show/
+'''
+
+class NumArray(object):
+
+    # DP : 动态规划
+    def __init__(self, nums):
+        """
+        :type nums: List[int]
+        """
+        if not nums: return
+        self.result = [0] * len(nums)
+        self.result[0] = nums[0]
+        for i in range(1, len(nums)):
+            # result[i] 的值为 nums[0] 到 nums[i] 的所有值之和
+            self.result[i] = self.result[i - 1] + nums[i]
+
+    def sumRange(self, i, j):
+        """
+        :type i: int
+        :type j: int
+        :rtype: int
+        """
+        if i == 0: return self.result[j]
+        else: return self.result[j] - self.result[i - 1]
+
+# Your NumArray object will be instantiated and called as such:
+# obj = NumArray(nums)
+# param_1 = obj.sumRange(i,j)
+```

docs/SUMMARY.md

@@ -79,6 +79,7 @@
     * [258.各位相加](LeetCode刷题之旅及题目解析/258.各位相加/258.各位相加.md)
     * [260.只出现一次的数字III](LeetCode刷题之旅及题目解析/260.只出现一次的数字III/260.只出现一次的数字III.md)
     * [283.移动零](LeetCode刷题之旅及题目解析/283.移动零/283.移动零.md)
+    * [303.区域和检索-数组不可变](LeetCode刷题之旅及题目解析/303.区域和检索-数组不可变/303.区域和检索-数组不可变.md)
     * [344.反转字符串](LeetCode刷题之旅及题目解析/344.反转字符串/344.反转字符串.md)
     * [345.反转字符串中的元音字母](LeetCode刷题之旅及题目解析/345.反转字符串中的元音字母/345.反转字符串中的元音字母.md)
     * [349.两个数组的交集](LeetCode刷题之旅及题目解析/349.两个数组的交集/349.两个数组的交集.md)