58 lines
1.2 KiB
Rust
58 lines
1.2 KiB
Rust
/**
|
|
* [303] Range Sum Query - Immutable
|
|
*/
|
|
pub struct Solution {}
|
|
|
|
// submission codes start here
|
|
|
|
struct NumArray {
|
|
prefix_array: 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 prefix_array = Vec::with_capacity(nums.len());
|
|
|
|
for (index, value) in nums.iter().enumerate() {
|
|
if index == 0 {
|
|
prefix_array.push(*value);
|
|
} else {
|
|
prefix_array.push(prefix_array[index - 1] + *value);
|
|
}
|
|
}
|
|
|
|
NumArray { prefix_array }
|
|
}
|
|
|
|
fn sum_range(&self, left: i32, right: i32) -> i32 {
|
|
let left = left as usize;
|
|
let right = right as usize;
|
|
|
|
return if left == 0 {
|
|
self.prefix_array[right]
|
|
} else {
|
|
self.prefix_array[right] - self.prefix_array[left - 1]
|
|
};
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Your NumArray object will be instantiated and called as such:
|
|
* let obj = NumArray::new(nums);
|
|
* let ret_1: i32 = obj.sum_range(left, right);
|
|
*/
|
|
|
|
// submission codes end
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn test_303() {}
|
|
}
|