一、問題:
Use the following method printPrimes() for questions a–d.
二、代碼
/******************************************************* * Finds and prints n prime integers * Jeff Offutt, Spring 2003 ******************************************************/ public static void printPrimes (int n) { int curPrime; // Value currently considered for primeness int numPrimes; // Number of primes found so far. boolean isPrime; // Is curPrime prime? int [] primes = new int [MAXPRIMES]; // The list of prime numbers. // Initialize 2 into the list of primes. primes [0] = 2; numPrimes = 1; curPrime = 2; while (numPrimes < n) { curPrime++; // next number to consider ... isPrime = true; for (int i = 0; i <= numPrimes-1; i++) { // for each previous prime. if (isDivisable(primes[i],curPrime)) { // Found a divisor, curPrime is not prime. isPrime = false; break; // out of loop through primes. } } if (isPrime) { // save it! primes[numPrimes] = curPrime; numPrimes++; } } // End while // Print all the primes out. for (int i = 0; i <= numPrimes-1; i++) { System.out.println ("Prime: " + primes[i]); } } // end printPrimes
三、解答
a、數據流圖如下:
b、數組越界時可能會發生錯誤
c、不經過while循環,使得 初始條件n=1
d、點覆蓋
{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16}
邊覆蓋
{(1.2),(2,3),(3,4),(4,5),(5,6),(6,7),(7,5),(6,8),(8,9),(9,10),(9,11),(10,2),(11,2),(2,12),(12,13),(13,14),(14,15),(15,13),(13,16)}
主路徑覆蓋
{(1,2,3,4,5,6,7),
(1,2,3,4,5,9,10),
(1,2,3,4,5,9,11),
(1,2,3,4,5,6,8,9,10),
(1,2,3,4,5,6,8,9,11),
(1,2,12,13,16),
(1,2,12,13,14,15),
(3,4,5,6,8,9,10,2,12,13,14,15),
(3,4,5,6,8,9,10,2,12,13,16),
(3,4,5,9,10,2,12,13,14,15),
(3,4,5,9,11,2,12,13,14,15),
(3,4,5,9,10,2,12,13,16),
(3,4,5,9,10,2,12,13,16),
(3,4,5,6,8,9,11,2,12,13,14,15),
(3,4,5,6,8,9,11,2,12,13,16),
(6,7,5,9,10,2,12,13,14,15),
(6,7,5,9,10,2,12,13,16),
(6,7,5,9,11,2,12,13,14,15),
(6,7,5,9,11,2,12,13,16),
(14,15,13,16),
(13,14,15,13),
(5,6,7,5),
(2,3,4,5,6,8,9,10,2),
(2,3,4,5,6,8,9,11,2),
(2,3,4,5,9,10,2)
(2,3,4,5,9,11,2)}
D、上次上機實驗的判斷三角形的程序
因為三角形的種類有三種,外加一種判斷輸入參數是否為正整數的返回值,因此主路徑測試需求有四個,測試四組用例(2,2,2),(2,3,3),(2,3,4),(-2,5,-6)。
即可完整覆蓋,覆蓋率達到100%;