四道水题，题目过于简单，实在没什么可讨论的。

10921 - Find the Telephone　　　　　　

 1 #include <stdio.h>
 2 int main()
 3 {
 4     char ch[100];
 5     int i;
 6     int code[26] = {2,2,2,3,3,3,4,4,4,5,5,5,6,6,6,7,7,7,7,8,8,8,9,9,9,9}; 
 7     while(scanf("%s", ch) == 1){
 8         for(i = 0; ch[i]; i++){
 9             if(ch[i] >= 'A' && ch[i] <= 'Z')
10                 printf("%d", code[ch[i] - 'A']);
11             else
12                 printf("%c", ch[i]);
13         }
14         printf("\n");
15     }
16     return 0;
17 }

10222 - Decode the Mad man

 1 #include <stdio.h>
 2 #include <string.h>
 3 int main()
 4 {
 5     char ch1[][20]={"`1234567890-=","qwertyuiop[]\\","asdfghjkl;'","zxcvbnm,./"};
 6     int c;    /*getchar函数的返回值就是int，否则无法返回-1*/
 7     int i, j, flag;
 8     while((c = getchar()) !=EOF){  /*对于不定容量的字符流，还是不要默认为字符串的好*/
 9         flag = 0;
10         if(c >= 'A' && c <= 'Z')
11             c += 32;
12         for(i = 0; i < 4; i++){
13             for(j = 0; ch1[i][j]; j++)
14                 if(ch1[i][j] ==    c){
15                     flag = 1;   /*找到相应字符*/
16                     putchar(ch1[i][j-2]);
17                     break;
18                 }
19             if(flag)
20                 break;
21         }
22         if(flag == 0)
23             putchar(c);
24     }
25     return 0;
26 }

686 - Goldbach's Conjecture (II)

 1 #include <stdio.h>
 2 #include <math.h>
 3 int is_prime(int a);
 4 int main()
 5 {
 6     int n, m, num, flag, i;
 7     while(scanf("%d", &n) == 1  && n){
 8         num = 0;
 9         flag = 0;
10         m = n;
11         n /= 2;
12         for(i = 2; i <= n; i++)
13             if(is_prime(i) && is_prime(m-i))
14                 num++;
15         printf("%d\n", num);
16     }
17     return 0;    
18 }
19 int is_prime(int a)
20 {
21     int flag = 1, i;
22     int n = (int)sqrt((double)a);
23     for(i = 2; i <= n; i++)
24         if(a % i == 0){
25             flag = 0;
26             break;
27         }
28     return flag;
29 }

10970 - Big Chocolate

 1 #include <stdio.h>
 2 static int cut(int n, int m);
 3 int main()
 4 {
 5     int n, m;
 6     while(scanf("%d%d", &n, &m) == 2)
 7         printf("%d\n", cut(n,m));
 8     return 0;
 9 }
10 static int cut(int n, int m)
11 {
12     return (n - 1) + n * (m - 1);
13 }