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p0001_two_sum.rs
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p0001_two_sum.rs
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// 1. Two Sum
// Easy
// Given an array of integers, return indices of the two numbers such that they add up to a specific target.
// You may assume that each input would have exactly one solution, and you may not use the same element twice.
// Example:
// Given nums = [2, 7, 11, 15], target = 9,
// Because nums[0] + nums[1] = 2 + 7 = 9,
// return [0, 1].
pub struct Solution {}
use std::collections::HashMap;
impl Solution {
pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
// 暴力枚举法
// let len = nums.len();
// for i in 0..len {
// for j in i+1..len {
// if nums[i] + nums[j] == target {
// return vec![i as i32, j as i32];
// }
// }
// }
// vec![]
// 利用HashMap, 一次遍历
let mut map = HashMap::new();
for (index, num) in nums.iter().enumerate() {
// 这里必须得使用&符号, other_index也必须使用*号
match map.get(&(target-num)) {
None => { map.insert(num, index); },
Some(other_index) => { return vec![*other_index as i32, index as i32] },
}
}
vec![]
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn two_sum_test() {
assert_eq!(vec![0, 1], Solution::two_sum(vec![2, 7, 11, 15], 9));
assert_eq!(vec![1, 2], Solution::two_sum(vec![3, 2, 4], 6));
}
}