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Sunday, 28 August 2016

Chapter 8 Exercise 3, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

 
*8.3 (Sort students on grades) Rewrite Listing 8.2, GradeExam.java, to display the students in increasing order of the number of correct answers.


public class ProgramingEx8_3 {
 /** Main method */
   public static void main(String args[]) {
     // Students' answers to the questions
     char[][] answers = {
       {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
       {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
       {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
       {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
       {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
       {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
       {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
       {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}};
 
     // Key to the questions
     char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
     //Array to keep result
     int[][] result = new int[answers.length][2];
 
     // Grade all answers
     for (int i = 0; i < answers.length; i++) {
       // Grade one student
       int correctCount = 0;
       for (int j = 0; j < answers[i].length; j++) {
         if (answers[i][j] == keys[j])
           correctCount++;
       }
        result[i][0] = i;
        result[i][1] = correctCount;
           
     }
     selectionSort(result);
     //printing out result
      
     for (int j = 0; j < result.length; j++) {
         System.out.println("Student " + result[j][0] + "'s correct count is " +
           result[j][1]);
  }
      
 
   }      
    
   public static void selectionSort(int[][] list) {
   for (int i = 0; i < list.length - 1; i++) {
    // Find the minimum in the list[i..list.length-1]
    int currentMin = list[i][1];
    int currentMinIndex = i;
 
    for (int j = i + 1; j < list.length; j++) {
     if (currentMin > list[j][1]) {
      currentMin = list[j][1];
      currentMinIndex = j;
     }
    }
 
    // Swap list[i] with list[currentMinIndex] if necessary
    if (currentMinIndex != i) {
     list[currentMinIndex][1] = list[i][1];
     list[i][1] = currentMin;
     list[currentMinIndex][0] = list[i][0];
     list[i][0] = currentMinIndex;
 
    }
   }
  }
}

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