src/bin/range-sum-query-immutable.rs

bestgopher · bestgopher · commit a2aea480352b · 2021-07-19T21:16:58.000+08:00
diff --git a/src/bin/range-sum-query-immutable.rs b/src/bin/range-sum-query-immutable.rs
@@ -0,0 +1,42 @@
+fn main() {}
+
+struct Solution;
+
+
+/**
+ * Your NumArray object will be instantiated and called as such:
+ * let obj = NumArray::new(nums);
+ * let ret_1: i32 = obj.sum_range(left, right);
+ */
+struct NumArray {
+    sums: Vec<i32>
+}
+
+
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl NumArray {
+    fn new(nums: Vec<i32>) -> Self {
+        let mut sums = Vec::with_capacity(nums.len());
+
+        for i in 0..=nums.len() {
+            if i == 0 {
+                sums.push(0);
+            } else {
+                sums.push(nums[i] + sums[i - 1]);
+            }
+        }
+
+        Self { sums }
+    }
+
+    fn sum_range(&self, left: i32, right: i32) -> i32 {
+        if left == 0 {
+            self.sums[right as usize]
+        } else {
+            self.sums[right as usize] - self.sums[left as usize - 1usize]
+        }
+    }
+}
