题解 | #合并表记录#

use std::io::{self, *};
use std::collections::HashMap;

fn main() {
let mut input = String::new();
        std::io::stdin().read_line(&mut input).expect("input failed.");
        // println!("input {}", input);
        let num = input.trim().parse().expect("can not parse this num");
        let mut map = HashMap::new();
        for _ in 0..num {
            let mut input = String::new();
            std::io::stdin().read_line(&mut input).expect("input failed.");
            let arr: Vec<i32> = input.split_whitespace()
                                     .map(|s| s.parse().expect("input failed2"))
                                     .collect();
            match map.get(&arr[0]) {
                Some(num) => {
                    map.insert(arr[0], num+arr[1]);
                },
                None => {
                    map.insert(arr[0], arr[1]);
                },
            }
        }

        let mut keys: Vec<_> = map.keys().collect();
        keys.sort();

        // println!("result: ");

        for key in keys {
            if let Some(v) = map.get(key) {
                println!("{} {}", key, v);
            }
        }
}