Algorithm
lc1865_找出和为指定值的下标对
思路:
看数据范围就能知道需要遍历nums1, 然后去nums2的 count map 计数中去进行查找。
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use std::collections::HashMap;
struct FindSumPairs {
nums1: Vec<i32>,
nums2: Vec<i32>,
nums2_count: HashMap<i32, i32>,
}
/**
* `&self` means the method takes an immutable reference.
* If you need a mutable reference, change it to `&mut self` instead.
*/
impl FindSumPairs {
fn new(nums1: Vec<i32>, nums2: Vec<i32>) -> Self {
let mut nums2_count = HashMap::new();
for num in nums2.iter() {
*nums2_count.entry(*num).or_insert(0) += 1;
}
Self {
nums1,
nums2,
nums2_count,
}
}
fn add(&mut self, index: i32, val: i32) {
self.nums2[index as usize] += val;
*self.nums2_count.entry(self.nums2[index as usize]).or_insert(0) += 1;
*self.nums2_count.entry(self.nums2[index as usize] - val).or_insert(0) -= 1;
}
fn count(&self, tot: i32) -> i32 {
let mut count = 0;
for num in &self.nums1 {
count += self.nums2_count.get(&(tot - num)).unwrap_or(&0);
}
count
}
}
/**
* Your FindSumPairs object will be instantiated and called as such:
* let obj = FindSumPairs::new(nums1, nums2);
* obj.add(index, val);
* let ret_2: i32 = obj.count(tot);
*/
|
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