86 lines
2.1 KiB
Rust
86 lines
2.1 KiB
Rust
/**
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* [2080] Range Frequency Queries
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*/
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pub struct Solution {}
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// submission codes start here
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use std::collections::HashMap;
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struct RangeFreqQuery {
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frequency_map: HashMap<i32, Vec<usize>>,
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}
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/**
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* `&self` means the method takes an immutable reference.
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* If you need a mutable reference, change it to `&mut self` instead.
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*/
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impl RangeFreqQuery {
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fn new(arr: Vec<i32>) -> Self {
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let mut frequency_map = HashMap::new();
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for (i, v) in arr.into_iter().enumerate() {
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let entry = frequency_map.entry(v).or_insert(vec![]);
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entry.push(i);
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}
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Self { frequency_map }
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}
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fn query(&self, left: i32, right: i32, value: i32) -> i32 {
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let (left, right) = (left as usize, right as usize);
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if let Some(index) = self.frequency_map.get(&value) {
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let l = index.binary_search(&left);
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let r = index.binary_search(&right);
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let result = match l {
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Ok(l_ok) => match r {
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Ok(r_ok) => r_ok - l_ok + 1,
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Err(r_err) => r_err - l_ok,
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},
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Err(l_err) => match r {
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Ok(r_ok) => r_ok - l_err + 1,
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Err(r_err) => r_err - l_err,
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},
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};
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result as i32
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} else {
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0
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}
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}
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}
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/**
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* Your RangeFreqQuery object will be instantiated and called as such:
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* let obj = RangeFreqQuery::new(arr);
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* let ret_1: i32 = obj.query(left, right, value);
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*/
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// submission codes end
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_2080() {
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let query = RangeFreqQuery::new(vec![12, 33, 4, 56, 22, 2, 34, 33, 22, 12, 34, 56]);
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assert_eq!(1, query.query(1, 2, 4));
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assert_eq!(2, query.query(0, 11, 33));
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let query = RangeFreqQuery::new(vec![2, 2, 1, 2, 2]);
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// [2]
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assert_eq!(1, query.query(2, 4, 1));
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assert_eq!(1, query.query(1, 3, 1));
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assert_eq!(1, query.query(0, 2, 1));
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let query = RangeFreqQuery::new(vec![1, 1, 1, 2, 2]);
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// [0, 1, 2]
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assert_eq!(1, query.query(2, 2, 1));
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}
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}
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