題目內容

對題目的含義理解錯誤

看代碼~~我以為是統計一下多少人在那天，覺得這個pageNum沒大用，結果是我錯了……
下為代碼：

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int studentNum = scanner.nextInt();int pageNum = scanner.nextInt();int dayNum = scanner.nextInt();int[] dayArray = new int[dayNum];for (int i = 0; i < studentNum; i++) {for (int j = 0; j < pageNum; j++) {int temp = scanner.nextInt();dayArray[temp-1]++;}}StringBuilder result = new StringBuilder();for (int i = 0; i < dayNum-1; i++) {result.append(dayArray[i]).append(" ");}result.append(dayArray[dayNum-1]);System.out.println(result);scanner.close();} }

測試：

顯然，結果是不對的……

更正后的自測

結尾一個數不對，查看代碼，發現bug：

第一次提交——TLE警告

代碼是這樣的：

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int studentNum = scanner.nextInt();int pageNum = scanner.nextInt();int dayNum = scanner.nextInt();int[][] dayArray = new int[dayNum][pageNum];for (int i = 0; i < studentNum; i++) {for (int j = 0; j < pageNum; j++) {int temp = scanner.nextInt();dayArray[temp-1][j]++;}}StringBuilder result = new StringBuilder();for (int i = 0; i < dayNum-1; i++) {int count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[i][j] != 0) {count++;}}result.append(count).append(" ");}int count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[dayNum-1][j] != 0) {count++;}}result.append(count);System.out.println(result);scanner.close();} }

第二次提交——TLE×3暴擊

本蒟蒻沒想到，boolean比int還慢，醉了：

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int studentNum = scanner.nextInt();int pageNum = scanner.nextInt();int dayNum = scanner.nextInt();boolean[][] dayArray = new boolean[dayNum][pageNum];for (int i = 0; i < studentNum; i++) {for (int j = 0; j < pageNum; j++) {int temp = scanner.nextInt();dayArray[temp-1][j]=true;}}StringBuilder result = new StringBuilder();for (int i = 0; i < dayNum-1; i++) {int count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[i][j]) {count++;}}result.append(count).append(" ");}int count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[dayNum-1][j]) {count++;}}result.append(count);System.out.println(result);scanner.close();} }

第三次提交——RE，寧真狼

這次直接byte，我們既然不想優化算法，那就優化數據類型吧，哈哈：

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);byte studentNum = scanner.nextByte();byte pageNum = scanner.nextByte();byte dayNum = scanner.nextByte();byte[][] dayArray = new byte[dayNum][pageNum];for (int i = 0; i < studentNum; i++) {for (int j = 0; j < pageNum; j++) {int temp = scanner.nextInt();dayArray[temp-1][j]++;}}StringBuilder result = new StringBuilder();for (int i = 0; i < dayNum-1; i++) {byte count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[i][j] != 0) {count++;}}result.append(count).append(" ");}byte count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[dayNum-1][j] != 0) {count++;}}result.append(count);System.out.println(result);scanner.close();} }

盲測是超byte范圍了，可我真的忘了byte的大小誒，測一下~~

自檢：

復習一下，byte在-128~127，寧真行……

第四次提交——AC之道，在于Short

附上AC代碼

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);short studentNum = scanner.nextShort();short pageNum = scanner.nextShort();short dayNum = scanner.nextShort();short[][] dayArray = new short[dayNum][pageNum];for (int i = 0; i < studentNum; i++) {for (int j = 0; j < pageNum; j++) {int temp = scanner.nextInt();dayArray[temp-1][j]++;}}StringBuilder result = new StringBuilder();for (int i = 0; i < dayNum-1; i++) {short count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[i][j] != 0) {count++;}}result.append(count).append(" ");}short count = 0;for (int j = 0; j < pageNum; j++) {if (dayArray[dayNum-1][j] != 0) {count++;}}result.append(count);System.out.println(result);scanner.close();} }

總結

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