USASO Section1.1Your Ride Is Here[其他]

2017.5.18

题目：

输入两个由大写字母组成的字符串，A~Z分别转换为1~26，然后将其累乘，得到的两个乘积如果mod 47后相等则输出GO，否则输出STAY
SAMPLE INPUT (file ride.in)#

COMETQ
HVNGAT
OUTPUT FORMAT

A single line containing either the word “GO” or the word “STAY”.
SAMPLE OUTPUT (file ride.out)

GO
OUTPUT EXPLANATION

Converting the letters to numbers:
C O M E T Q
3 15 13 5 20 17
H V N G A T
8 22 14 7 1 20
then calculate the product mod 47:
3 * 15 * 13 * 5 * 20 * 17 = 994500 mod 47 = 27
8 * 22 * 14 * 7 * 1 * 20 = 344960 mod 47 = 27
Because both products evaluate to 27 (when modded by 47), the mission is ‘GO’.

题解：

乘积的取余等于取余的乘积，由此可以避免数据溢出。注意ASCII码和字符之间的转换，表内字符可以直接作为整数来计算，减去64即可。

代码：

/*ID: xcwhkh1LANG: CTASK: ride*/#include <stdio.h>char a[100002];char b[100002];int main () {    FILE *fin  = fopen ("ride.in", "r");    FILE *fout = fopen ("ride.out", "w");    fscanf (fin, "%s\n%s",a,b); /* the two input integers */    int sa=1,sb=1,i;    for(i=0;a[i]!='\0';i++)    sa=sa*(a[i]-64)%47;    for(i=0;b[i]!='\0';i++)    sb=sb*(b[i]-64)%47;    if(sa!=sb)    fprintf (fout,"STAY\n");    else    fprintf (fout,"GO\n");    return 0;}