RSA算法 :首先, 找出三個數, p, q, r, 其中 p, q 是兩個相異的質數, r 是與 (p-1)(q-1) 互質的數...... p, q, r 這三個數便是 person_key，接著, 找出 m, 使得 r^m == 1 mod (p-1)(q-1)..... 這個 m 一定存在, 因為 r 與 (p-1)(q-1) 互質, 用輾轉相除法就可以得到了..... 再來, 計算 n = pq....... m, n 這兩個數便是 public_key ，編碼過程是, 若資料為 a, 將其看成是一個大整數, 假設 a < n.... 如果 a >= n 的話, 就將 a 表成 s 進位 (s
5 ledblink -- 跑馬燈程序
該項目在SDT2.51下編譯調試。最簡單的demo程序，運行后3個發光二極管輪流點亮。
6 timerint -- 定時器中斷demo程序
該項目在SDT2.51下編譯調試。將子目錄timerint拷貝到c:\ 下。
該demo程序的主程序是while空循環，定時器中斷服務程序每500ms將3個LED反相。
在57600超級終端里也可以看到中斷發生時的信息。
7 uart -- 串口測試程序
該項目在SDT2.51下編譯調試。運行后在57600的超級終端里等待PC鍵盤的輸入，當按下 a 或 b 或 c 按鍵時，超級終端里將顯示 You Pressed a ,You Pressed b ,You Pressed c .
The government of a small but important country has decided that the alphabet needs to be streamlined and reordered. Uppercase letters will be eliminated. They will issue a royal decree in the form of a String of B and A characters. The first character in the decree specifies whether a must come ( B )Before b in the new alphabet or ( A )After b . The second character determines the relative placement of b and c , etc. So, for example, "BAA" means that a must come Before b , b must come After c , and c must come After d .
Any letters beyond these requirements are to be excluded, so if the decree specifies k comparisons then the new alphabet will contain the first k+1 lowercase letters of the current alphabet.
Create a class Alphabet that contains the method choices that takes the decree as input and returns the number of possible new alphabets that conform to the decree. If more than 1,000,000,000 are possible, return -1.
Definition
