[英]Finding the longest increasing contiguous subsequence
我正在尝试编写一个将序列作为数组的程序,然后打印最长的连续子序列及其长度。 在到目前为止(下面)编写的代码中,我设法通过longestForward方法实现了这一点。 但是,在分配规范中,我还被要求编写另一种方法longestBackwards,该方法可以完成完全相同的任务,即。 将打印完全相同的内容,但是它必须向后搜索原始数组。 这就是我遇到的困难。
我设法编写了一种方法,该方法仅打印最长连续子序列的最后两个成员,并且以相反的顺序打印(例如,对于数组4,5,6,它打印6、5)。 但是,它可以正确打印长度。
如果有人可以帮我弄清楚我做错了什么,将不胜感激。
import java.util.Scanner;
public class LongestSubsequence {
public static void main(String[] args) {
// Test array
int[] arr = {4, 5, 6};
longestForward(arr);
longestBackward(arr);
}
public static void longestForward(int[] arr)
{
int subSeqLength = 1;
int longest = 1;
int indexStart = 0;
int indexEnd = 0;
for (int i = 0; i < arr.length - 1; i++)
{
if (arr[i] < arr[i + 1] )//We need to check if the current is equal to the next
{
subSeqLength++;//if it is we increment
if (subSeqLength > longest)//we assign the longest and new bounds
{
longest = subSeqLength;
indexStart = i + 2 - subSeqLength;
indexEnd = i + 2;
}
}
else
subSeqLength = 1;//else re-initiate the straight length
}
System.out.println(longest);
for (int i = indexStart; i < indexEnd; i++)//print the sequence
System.out.print(arr[i] + ", ");
}
public static void longestBackward(int[] arr) {
int subSeqLength = 1;
int longest = 1;
int indexStart = 0;
int indexEnd = 0;
for (int i = arr.length - 1; i > 0; i--) {
if (arr[i] > arr[i - 1]) {
subSeqLength++;
if (subSeqLength > longest) {
longest = subSeqLength;
indexStart = i + (subSeqLength - 1);
indexEnd = i - 1;
}
} // Else re-initiate the length
else {
subSeqLength = 1;
}
}
System.out.println("");
// Print the sequence
System.out.println(longest);
for (int i = indexStart-1; i > indexEnd; i--) {
System.out.print(arr[i] + ", ");
}
}
}
for (int i = arr.length - 1; i > 0; i--) {
if (arr[i] > arr[i - 1]) {
subSeqLength++;
if (subSeqLength > longest) {
longest = subSeqLength;
indexStart = i + (subSeqLength - 1);
indexEnd = i - 1;
}
} // Else re-initiate the length
for循环不应该看起来像这样:
for (int i = arr.length - 1; i >= 0; i--) {
您没有收到arr [0],因为您要在arr [1]之后停止。
只是为了澄清..为什么您不能花最长的时间来扭转它呢? 最长的前进会不会是最长的后退的逆转?
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