原文:
给定一个由 n 个元素组成的数组。任务是以这样的方式打印数组元素:前两个元素按升序排列，后三个按降序排列，后四个按升序排列，依此类推。
示例:
输入 : arr = {2，6，2，4，0，1，4，8，2，0，0，5，2，2} 输出:0 0 8 6 5 0 1 2 4 2 2 2 2
输入 : arr = {1，2，3，4，5，6} 输出 : 1 2 6 5 4 3
来源 : 思路是使用 。首先按递增顺序对数组进行排序，并保持两个指针和，其中是按递增顺序打印数组，是按递减顺序打印数组。保留一个变量以指定迭代中要打印的元素数量，并保留一个变量标志以交替地在升序和降序打印之间切换。
下面是上述方法的实现:
c
// c program to print array elements in
// alternative increasing and decreasing
// order
#include
using namespace std;
// function to print array elements in
// alternative increasing and decreasing
// order
void printarray(int arr[], int n)
{
// first sort the array in increasing order
sort(arr, arr n);
int l = 0, r = n - 1, flag = 0, i;
// start with 2 elements in
// increasing order
int k = 2;
// till all the elements are not printed
while (l <= r) {
// printing the elements in
// increasing order
if (flag == 0) {
for (i = l; i < l k && i <= r; i )
cout << arr[i] << " ";
flag = 1;
l = i;
}
else // printing the elements in
// decreasing order
{
for (i = r; i > r - k && i >= l; i--)
cout << arr[i] << " ";
flag = 0;
r = i;
}
// increasing the number of elements
// to printed in next iteration
k ;
}
}
// driver code
int main()
{
int n = 6;
int arr[] = { 1, 2, 3, 4, 5, 6 };
printarray(arr, n);
return 0;
}
java 语言(一种计算机语言，尤用于创建网站)
// java program to print array elements in
// alternative increasing and decreasing
// order
import java.util.*;
class solution
{
// function to print array elements in
// alternative increasing and decreasing
// order
static void printarray(int arr[], int n)
{
// first sort the array in increasing order
arrays.sort(arr);
int l = 0, r = n - 1, flag = 0, i;
// start with 2 elements in
// increasing order
int k = 2;
// till all the elements are not printed
while (l <= r) {
// printing the elements in
// increasing order
if (flag == 0) {
for (i = l; i < l k && i <= r; i )
system.out.print(arr[i] " ");
flag = 1;
l = i;
}
else // printing the elements in
// decreasing order
{
for (i = r; i > r - k && i >= l; i--)
system.out.print(arr[i] " ");
flag = 0;
r = i;
}
// increasing the number of elements
// to printed in next iteration
k ;
}
}
// driver code
public static void main(string args[])
{
int n = 6;
int arr[] = { 1, 2, 3, 4, 5, 6 };
printarray(arr, n);
}
}
//contributed by arnab kundu
python 3
# python 3 program to print array elements
# in alternative increasing and decreasing
# order
# function to print array elements in
# alternative increasing and decreasing
# order
def printarray(arr, n):
# first sort the array in
# increasing order
arr.sort()
l = 0
r = n - 1
flag = 0
# start with 2 elements in
# increasing order
k = 2
# till all the elements are not printed
while (l <= r) :
# printing the elements in
# increasing order
if (flag == 0):
i = l
while i < l k and i <= r:
print(arr[i], end = " ")
i = 1
flag = 1
l = i
else: # printing the elements in
# decreasing order
i = r
while i > r - k and i >= l:
print(arr[i], end = " ")
i -= 1
flag = 0
r = i
# increasing the number of elements
# to printed in next iteration
k = 1
# driver code
if __name__ == "__main__":
n = 6
arr = [ 1, 2, 3, 4, 5, 6 ]
printarray(arr, n)
# this code is contributed by ita_c
c
// c# program to print array elements in
// alternative increasing and decreasing
// order
using system;
class gfg{
// function to print array elements in
// alternative increasing and decreasing
// order
static void printarray(int []arr, int n)
{
// first sort the array
// in increasing order
array.sort(arr);
int l = 0, r = n - 1, flag = 0, i;
// start with 2 elements in
// increasing order
int k = 2;
// till all the elements
// are not printed
while (l <= r) {
// printing the elements in
// increasing order
if (flag == 0) {
for (i = l; i < l k && i <= r; i )
console.write(arr[i] " ");
flag = 1;
l = i;
}
else
// printing the elements in
// decreasing order
{
for (i = r; i > r - k && i >= l; i--)
console.write(arr[i] " ");
flag = 0;
r = i;
}
// increasing the number of elements
// to printed in next iteration
k ;
}
}
// driver code
static public void main ()
{
int n = 6;
int []arr = { 1, 2, 3, 4, 5, 6 };
printarray(arr, n);
}
}
// this code is contributed by sach_code
服务器端编程语言（professional hypertext preprocessor 的缩写）
$r - $k &&
$i >= $l; $i--)
echo $arr[$i] , " ";
$flag = 0;
$r = $i;
}
// increasing the number of elements
// to printed in next iteration
$k ;
}
}
// driver code
$n = 6;
$arr = array( 1, 2, 3, 4, 5, 6 );
printarray($arr, $n);
// this code is contributed by jit_t
?>
java 描述语言
output:
1 2 6 5 4 3
时间复杂度:o(nlogn) t3】辅助空间: o(1)
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