归并排序的核心思想是分治，把一个复杂问题拆分成若干个子问题来求解。
归并排序的算法思想是：把数组从中间划分为两个子数组，一直递归地把子数组划分成更小的数组，直到子数组里面只有一个元素的时候开始排序。排序的方法就是按照大小顺序合并两个元素。接着依次按照递归的顺序返回，不断合并排好序的数组，直到把整个数组排好序。
归并排序算法模板：
void mergeSort(int[] nums, int left, int right) {
if (left >= right) {
return;
}
int mid = (left + right) >>> 1;
mergeSort(nums, left, mid);
mergeSort(nums, mid + 1, right);
int i = left, j = mid + 1, k = 0;
while (i <= mid && j <= right) {
if (nums[i] <= nums[j]) {
tmp[k++] = nums[i++];
} else {
tmp[k++] = nums[j++];
}
}
while (i <= mid) {
tmp[k++] = nums[i++];
}
while (j <= right) {
tmp[k++] = nums[j++];
}
for (i = left, j = 0; i <= right; ++i, ++j) {
nums[i] = tmp[j];
}
}给定你一个长度为 n 的整数数列。
请你使用归并排序对这个数列按照从小到大进行排序。
并将排好序的数列按顺序输出。
输入格式
输入共两行，第一行包含整数 n。
第二行包含 n 个整数（所有整数均在 1∼10^9 范围内），表示整个数列。
输出格式
输出共一行，包含 n 个整数，表示排好序的数列。
数据范围
1≤n≤100000
输入样例：
5
3 1 2 4 5
输出样例：
1 2 3 4 5
N = int(input())
nums = list(map(int, input().split()))
def merge_sort(nums, left, right):
if left >= right:
return
mid = (left + right) >> 1
merge_sort(nums, left, mid)
merge_sort(nums, mid + 1, right)
tmp = []
i, j = left, mid + 1
while i <= mid and j <= right:
if nums[i] <= nums[j]:
tmp.append(nums[i])
i += 1
else:
tmp.append(nums[j])
j += 1
while i <= mid:
tmp.append(nums[i])
i += 1
while j <= right:
tmp.append(nums[j])
j += 1
j = 0
for i in range(left, right + 1):
nums[i] = tmp[j]
j += 1
merge_sort(nums, 0, N - 1)
print(' '.join(list(map(str, nums))))import java.util.Scanner;
public class Main {
private static int[] tmp = new int[100010];
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int[] nums = new int[n];
for (int i = 0; i < n; ++i) {
nums[i] = sc.nextInt();
}
mergeSort(nums, 0, n - 1);
for (int i = 0; i < n; ++i) {
System.out.printf("%d ", nums[i]);
}
}
public static void mergeSort(int[] nums, int left, int right) {
if (left >= right) {
return;
}
int mid = (left + right) >>> 1;
mergeSort(nums, left, mid);
mergeSort(nums, mid + 1, right);
int i = left, j = mid + 1, k = 0;
while (i <= mid && j <= right) {
if (nums[i] <= nums[j]) {
tmp[k++] = nums[i++];
} else {
tmp[k++] = nums[j++];
}
}
while (i <= mid) {
tmp[k++] = nums[i++];
}
while (j <= right) {
tmp[k++] = nums[j++];
}
for (i = left, j = 0; i <= right; ++i, ++j) {
nums[i] = tmp[j];
}
}
}var buf = '';
process.stdin.on('readable', function () {
var chunk = process.stdin.read();
if (chunk) buf += chunk.toString();
});
let getInputArgs = line => {
return line.split(' ').filter(s => s !== '').map(x => parseInt(x));
}
function mergeSort(nums, left, right) {
if (left >= right) {
return;
}
const mid = (left + right) >> 1;
mergeSort(nums, left, mid);
mergeSort(nums, mid + 1, right);
let i = left;
let j = mid + 1;
let tmp = [];
while (i <= mid && j <= right) {
if (nums[i] <= nums[j]) {
tmp.push(nums[i++]);
} else {
tmp.push(nums[j++]);
}
}
while (i <= mid) {
tmp.push(nums[i++]);
}
while (j <= right) {
tmp.push(nums[j++]);
}
for (i = left, j = 0; i <= right; ++i, ++j) {
nums[i] = tmp[j];
}
}
process.stdin.on('end', function () {
buf.split('\n').forEach(function (line, lineIdx) {
if (lineIdx % 2 === 1) {
nums = getInputArgs(line);
mergeSort(nums, 0, nums.length - 1);
console.log(nums.join(' '));
}
});
});package main
import "fmt"
func mergeSort(nums []int, left, right int) {
if left >= right {
return
}
mid := (left + right) >> 1
mergeSort(nums, left, mid)
mergeSort(nums, mid+1, right)
i, j := left, mid+1
tmp := make([]int, 0)
for i <= mid && j <= right {
if nums[i] <= nums[j] {
tmp = append(tmp, nums[i])
i++
} else {
tmp = append(tmp, nums[j])
j++
}
}
for i <= mid {
tmp = append(tmp, nums[i])
i++
}
for j <= right {
tmp = append(tmp, nums[j])
j++
}
for i, j = left, 0; i <= right; i, j = i+1, j+1 {
nums[i] = tmp[j]
}
}
func main() {
var n int
fmt.Scanf("%d\n", &n)
nums := make([]int, n)
for i := 0; i < n; i++ {
fmt.Scanf("%d", &nums[i])
}
mergeSort(nums, 0, n-1)
for _, v := range nums {
fmt.Printf("%d ", v)
}
}