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53 lines
1.5 KiB
Rust
53 lines
1.5 KiB
Rust
/*
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* File: two_sum.rs
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* Created Time: 2023-01-14
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* Author: xBLACICEx (xBLACKICEx@outlook.com), codingonion (coderonion@gmail.com)
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*/
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use hello_algo_rust::include::print_util;
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use std::collections::HashMap;
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/* 方法 1：総当たり列挙 */
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pub fn two_sum_brute_force(nums: &Vec<i32>, target: i32) -> Option<Vec<i32>> {
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let size = nums.len();
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// 2重ループのため、時間計算量は O(n^2)
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for i in 0..size - 1 {
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for j in i + 1..size {
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if nums[i] + nums[j] == target {
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return Some(vec![i as i32, j as i32]);
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}
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}
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}
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None
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}
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/* 方法 2：補助ハッシュテーブル */
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pub fn two_sum_hash_table(nums: &Vec<i32>, target: i32) -> Option<Vec<i32>> {
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// 補助ハッシュテーブルを使用し、空間計算量は O(n)
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let mut dic = HashMap::new();
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// 単一ループで、時間計算量は O(n)
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for (i, num) in nums.iter().enumerate() {
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match dic.get(&(target - num)) {
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Some(v) => return Some(vec![*v as i32, i as i32]),
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None => dic.insert(num, i as i32),
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};
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}
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None
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}
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fn main() {
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// ======= Test Case =======
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let nums = vec![2, 7, 11, 15];
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let target = 13;
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// ====== Driver Code ======
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// 方法 1
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let res = two_sum_brute_force(&nums, target).unwrap();
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print!("方法1 res = ");
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print_util::print_array(&res);
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// 方法 2
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let res = two_sum_hash_table(&nums, target).unwrap();
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print!("\n方法2 res = ");
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print_util::print_array(&res);
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}
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