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@djhworld
Created December 29, 2018 20:15
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package main
import (
"bufio"
"fmt"
"os"
)
type Counter struct {
uniqueItems map[string]int
}
func NewCounter() *Counter {
c := new(Counter)
c.uniqueItems = make(map[string]int)
return c
}
func (c *Counter) Add(item string) {
if _, ok := c.uniqueItems[item]; !ok {
c.uniqueItems[item] = 1
} else {
c.uniqueItems[item] += 1
}
}
func (c *Counter) Render() {
for k, v := range c.uniqueItems {
fmt.Printf("%d\t%s\n", v, k)
}
}
func main() {
counter := NewCounter()
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
counter.Add(scanner.Text())
}
counter.Render()
}
use std::collections::HashMap;
use std::io;
struct Counter {
items: HashMap<String, usize>,
}
impl Counter {
fn new() -> Counter {
return Counter {
items: HashMap::with_capacity(1000),
};
}
fn add(&mut self, st: String) {
let x = self.items.entry(st).or_insert(0);
*x += 1;
}
fn render(&self) {
for (key, val) in &self.items {
println!("{}\t{}", val, key);
}
}
}
fn main() {
let mut c = Counter::new();
loop {
let mut line = String::new();
let r = io::stdin().read_line(&mut line);
match r {
Ok(0) => break,
Ok(_) => {
line.pop(); //strip newline char
c.add(line);
}
Err(err) => {
println!("{}", err);
break;
}
};
}
c.render();
}
@kellenff
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@Freaky good point! Your mention of allocation gave me the idea to look into refactoring the Counter to take a string slice and use that as the key instead of an owned String. This resulted in about a 34% improvement in counting performance over the get_mut implementation using owned Strings. I haven't looked into the performance implications of reading all of stdin before doing the counting, instead of using buffered reads. I suspect that clearing the buffer on each line read would incur some overhead, though. Interesting stuff.

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