如何比这更有效地(从内存)从控制台读取 int 值:
BufferedReader in ...
number = Integer.parseInt(in.readLine());
当我使用readLine()
并将其解析为int时,java创建许多String对象并消耗内存。我尝试使用 Scanner 和方法 nextInt() ,但这种方法也不是那么有效。
P.S I need read > 1000_000 values and I have memory limit.
编辑任务的完整代码
import java.io.*;
public class Duplicate {
public static void main(String[] args) throws IOException {
int last = 0;
boolean b = false;
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(reader.readLine());
for (int i = 0; i < n; i++) {
int number =Integer.parseInt(reader.readLine());
if (number == 0 && !b) {
System.out.println(0);
b = true;
}
if (number == last) continue;
last = number;
System.out.print(last);
}
}
}
并重写变体:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
public class Duplicate {
public static void main(String[] args) throws IOException {
int last = 0;
boolean b = false;
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int nextInt = getNextInt(reader);
for (int i = 0; i < nextInt; i++) {
int number = getNextInt(reader);
if (number == 0 && !b) {
System.out.println(0);
b = true;
}
if (number == last) continue;
b = true;
last = number;
System.out.println(last);
}
}
static int getNextInt(Reader in) throws IOException {
int c;
boolean negative = false;
do {
c = in.read();
if (!Character.isDigit(c)) {
negative = c == '-';
}
} while (c != -1 && !Character.isDigit(c));
if (c == -1) return Integer.MIN_VALUE;
int num = Character.getNumericValue(c);
while ((c = in.read()) != -1 && Character.isDigit(c)) {
num = 10 * num + Character.getNumericValue(c);
}
return negative ? -num : num;
}
}
两个选项都不会从内存中传递(((
编辑2我尝试分析
int number = getRandom();
并从 1000000 开始
和飞溅GC
最佳答案
您可以一次从 in
读取一个字符,检查它是否是数字,然后将其累加为一个数字。像这样的东西:
int getNextInt(Reader in) throws IOException {
int c;
boolean negative = false;
do {
c = in.read();
if (!Character.isDigit(c)) { negative = c == '-' };
} while (c != -1 && !Character.isDigit(c));
if (c == -1) return Integer.MIN_VALUE; // Some sentinel to indicate nothing found.
int num = Character.getNumericValue(c);
while ((c = in.read()) != -1 && Character.isDigit(c)) {
num = 10 * num + Character.getNumericValue(c);
}
return negative ? -num : num;
}
当然,这是令人难以置信的原始解析。但您也许可以将此代码作为基础并根据需要进行调整。
关于java - 更有效地从控制台读取 int 值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54323425/