57 lines
1.1 KiB
Plaintext
57 lines
1.1 KiB
Plaintext
/*
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file name: factorUsingIterative.c
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Description: Factorial numbers count using iterative
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利用迴圈做N階乘的計算
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*/
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#include <stdio.h>
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#include <ctype.h>
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#include <stdlib.h>
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/* 函數原型宣告 */
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long Factorial(long);
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void flushBuffer(void);
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int main()
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{
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char ch;
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long n;
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printf("-----Factorial counting using Iterative-----");
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do {
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printf("\nEnter a number(0 <= n <= 12) to count n!: ");
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scanf("%ld",&n);
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flushBuffer();
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if (n < 0 || n > 12)
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printf("Input out of range!\n");
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else
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printf("%ld! = %ld\n", n, Factorial(n));
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printf("Continue(y/n)? ");
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ch = toupper(getchar());
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} while (ch == 'Y');
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return 0;
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}
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long Factorial(long n)
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{
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long sum = 1;
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int i;
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if (n == 0 || n ==1) /* 當 n=0 或 n=1 時, 0!=1, 1!=1 */
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return (1); /* 故直接傳回1 */
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else {
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for (i = 2; i<= n; i++) /* sum 記錄目前階乘之和 */
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sum *= i; /* sum 與 i 相乘之和放回 sum 中 */
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}
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return (sum);
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}
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void flushBuffer()
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{
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while (getchar() != '\n') {
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continue;
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}
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}
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