algorithm/hello-algo
1
0
Fork 0
mirror of https://github.com/krahets/hello-algo.git synced 2025-11-04 06:07:20 +08:00
Code Issues Packages Projects Releases Wiki Activity

refactor: re-implement the rust codes of merge sort (#891)

Browse Source
This commit is contained in:
易春风
2023-10-26 22:24:02 +08:00
committed by GitHub
parent 08311f954a
commit 3628b40f44
1 changed files with 36 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

67
codes/rust/chapter_sorting/merge_sort.rs
View File

@ -5,45 +5,49 @@
*/ */
/* 合并左子数组和右子数组 */ /* 合并左子数组和右子数组 */
// 左子数组区间 [left, mid]
// 右子数组区间 [mid + 1, right]
fn merge(nums: &mut [i32], left: usize, mid: usize, right: usize) { fn merge(nums: &mut [i32], left: usize, mid: usize, right: usize) {
// 初始化辅助数组 // 左子数组区间 [left, mid], 右子数组区间 [mid+1, right]
let tmp: Vec<i32> = nums[left..right + 1].to_vec(); // 创建一个临时数组 tmp ，用于存放合并后的结果
// 左子数组的起始索引和结束索引 let tmp_size = right - left + 1;
let (left_start, left_end) = (left - left, mid - left); let mut tmp = vec![0; tmp_size];
// 右子数组的起始索引和结束索引 // 初始化左子数组和右子数组的起始索引
let (right_start, right_end) = (mid + 1 - left, right-left); let (mut i, mut j, mut k) = (left, mid + 1, 0);
// i, j 分别指向左子数组、右子数组的首元素 // 当左右子数组都还有元素时，比较并将较小的元素复制到临时数组中
let (mut l_corrent, mut r_corrent) = (left_start, right_start); while i <= mid && j <= right {
// 通过覆盖原数组 nums 来合并左子数组和右子数组 if nums[i] <= nums[j] {
for k in left..right + 1 { tmp[k] = nums[j];
// 若“左子数组已全部合并完”，则选取右子数组元素，并且 j++ i += 1;
if l_corrent > left_end { } else {
nums[k] = tmp[r_corrent]; tmp[k] = nums[j];
r_corrent += 1; j += 1;
}
// 否则，若“右子数组已全部合并完”或“左子数组元素 <= 右子数组元素”，则选取左子数组元素，并且 i++
else if r_corrent > right_end || tmp[l_corrent] <= tmp[r_corrent] {
nums[k] = tmp[l_corrent];
l_corrent += 1;
}
// 否则，若“左右子数组都未全部合并完”且“左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++
else {
nums[k] = tmp[r_corrent];
r_corrent += 1;
} }
k += 1;
}
// 将左子数组和右子数组的剩余元素复制到临时数组中
while i <= mid {
tmp[k] = nums[i];
k += 1;
i += 1;
}
while j <= right {
tmp[k] = nums[j];
k += 1;
j += 1;
}
// 将临时数组 tmp 中的元素复制回原数组 nums 的对应区间
for k in 0..tmp_size {
nums[left + k] = tmp[k];
} }
} }
/* 归并排序 */ /* 归并排序 */
fn merge_sort(left: usize, right: usize, nums: &mut [i32]) { fn merge_sort(nums: &mut [i32], left: usize, right: usize) {
// 终止条件 // 终止条件
if left >= right { return; } // 当子数组长度为 1 时终止递归 if left >= right { return; } // 当子数组长度为 1 时终止递归
// 划分阶段 // 划分阶段
let mid = (left + right) / 2; // 计算中点 let mid = (left + right) / 2; // 计算中点
merge_sort(left, mid, nums); // 递归左子数组 merge_sort(nums, left, mid); // 递归左子数组
merge_sort(mid + 1, right, nums); // 递归右子数组 merge_sort(nums, mid + 1, right); // 递归右子数组
// 合并阶段 // 合并阶段
merge(nums, left, mid, right); merge(nums, left, mid, right);
} }
@ -52,6 +56,7 @@ fn merge_sort(left: usize, right: usize, nums: &mut [i32]) {
fn main() { fn main() {
/* 归并排序 */ /* 归并排序 */
let mut nums = [7, 3, 2, 6, 0, 1, 5, 4]; let mut nums = [7, 3, 2, 6, 0, 1, 5, 4];
merge_sort(0, nums.len() - 1, &mut nums); let right = nums.len() - 1;
merge_sort(&mut nums, 0, right);
println!("归并排序完成后 nums = {:?}", nums); println!("归并排序完成后 nums = {:?}", nums);
} }