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10212 : The Last Non-zero Digit

10212 : The Last Non-zero Digit. ★★★☆☆ 題組： Problem Set Archive with Online Judge 題號： 10212 : The Last Non-zero Digit 解題者： 陳秉躍 解題日期： 20 14 年 5 月 22 日 題意： 給 你 2 個整數 N 、 M ， N 個不同的東西找出 M 個東西排列不同的方式，印出最後一個不為 0 的數字。 N （ 0 <= N <= 2 * 10 7 ） ， M （ 0 <= M <= N ）.

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10212 : The Last Non-zero Digit

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  1. 10212 : The Last Non-zero Digit • ★★★☆☆ • 題組：Problem Set Archive with Online Judge • 題號：10212 : The Last Non-zero Digit • 解題者：陳秉躍 • 解題日期：2014年5月22日 • 題意：給你2個整數N、M，N個不同的東西找出M個東西排列不同的方式，印出最後一個不為0的數字。N（0 <= N <= 2*107），M（0 <= M <= N）

  2. 題意範例：10 10 81055256 2 • 解法：M> 0 : ( N * (N - 1) * (N - 2) … (N - M+1 ) )%10M = 0 : 1%10可是因為N最大等於2*107 =>大數運算 ?只需要long longint，因為題目只要求印出最後一個不為0的數字每次乘法計算後的結果1. 個位數字為0，就除以10，直到個位數字不為02.mod 1010最後 mod 10 以後 印出來

  3. 解法範例：106 10 * 9 * 8 * 7 * 6 * 510 * 9=90 => 99 * 8=72 => 7272 * 7=504 => 504504 * 6=3024 => 30243024 * 5=15120 => 1512ans = 2 • 討論：

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