2013
11-12

# Barbara Bennett’s Wild Numbers

A wild number is a string containing digits and question marks (like 36?1?8). A number X matches a wild number W if they have the same length, and every non-question mark character in X is equal to the character in the same position in W (it means that you can replace a question mark with any digit). For example, 365198 matches the wild number 36?1?8, but 360199, 361028, or 36128 does not. Write a program that reads a wild number W and a number X from input, both of length n, and determines the number of n-digit numbers that match W and are greater than X.

There are multiple test cases in the input. Each test case consists of two lines of the same length. The first line contains a wild number W, and the second line contains an integer number X. The length of input lines is between 1 and 10 characters. The last line of input contains a single character #.

For each test case, write a single line containing the number of n-digit numbers matching W and greater than X (n is the length of W and X).

36?1?8
236428
8?3
910
?
5
#


100
0
4


//* @author 洪晓鹏<[email protected]/* <![CDATA[ */!function(t,e,r,n,c,a,p){try{t=document.currentScript||function(){for(t=document.getElementsByTagName('script'),e=t.length;e--;)if(t[e].getAttribute('data-cfhash'))return t[e]}();if(t&&(c=t.previousSibling)){p=t.parentNode;if(a=c.getAttribute('data-cfemail')){for(e='',r='0x'+a.substr(0,2)|0,n=2;a.length-n;n+=2)e+='%'+('0'+('0x'+a.substr(n,2)^r).toString(16)).slice(-2);p.replaceChild(document.createTextNode(decodeURIComponent(e)),c)}p.removeChild(t)}}catch(u){}}()/* ]]> */>
import java.io.IOException;

public class Main {

/**
* @param args
* @throws IOException
*/
public static int count(String a, String b) {
int len = a.length();
int result = 1;
for (int i = 0; i < len; i++) {
if (Character.isDigit(a.charAt(i))) {
if (a.charAt(i) > b.charAt(i)) {
for (int j = i + 1; j < len; j++) {
if (a.charAt(j) == '?')
result *= 10;
}
return result;
}
if (a.charAt(i) < b.charAt(i))
return 0;
} else {
if (len == i + 1)
return '9' - b.charAt(i);
else {
String new_a = a.substring(i + 1);
String new_b = b.substring(i + 1);
for (int j = i + 1; j < len; j++) {
if (a.charAt(j) == '?')
result *= 10;
}
return ('9' - b.charAt(i)) * result + count(new_a, new_b);
}
}
}
return 0;
}

public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
while (true) {
if (wild.equals("#"))
break;
System.out.println(count(wild, num));
}
}

}

1. 5.1处，反了；“上一个操作符的优先级比操作符ch的优先级大，或栈是空的就入栈。”如代码所述，应为“上一个操作符的优先级比操作符ch的优先级小，或栈是空的就入栈。”

2. 这道题这里的解法最坏情况似乎应该是指数的。回溯的时候
O(n) = O(n-1) + O(n-2) + ….
O(n-1) = O(n-2) + O(n-3)+ …
O(n) – O(n-1) = O(n-1)
O(n) = 2O(n-1)

3. 约瑟夫也用说这么长……很成熟的一个问题了，分治的方法解起来o(n)就可以了，有兴趣可以看看具体数学的第一章，关于约瑟夫问题推导出了一系列的结论，很漂亮

4. #include <stdio.h>
int main()
{
int n,p,t[100]={1};
for(int i=1;i<100;i++)
t =i;
while(scanf("%d",&n)&&n!=0){
if(n==1)
printf("Printing order for 1 pages:nSheet 1, front: Blank, 1n");
else {
if(n%4) p=n/4+1;
else p=n/4;
int q=4*p;
printf("Printing order for %d pages:n",n);
for(int i=0;i<p;i++){
printf("Sheet %d, front: ",i+1);
if(q>n) {printf("Blank, %dn",t[2*i+1]);}
else {printf("%d, %dn",q,t[2*i+1]);}
q–;//打印表前
printf("Sheet %d, back : ",i+1);
if(q>n) {printf("%d, Blankn",t[2*i+2]);}
else {printf("%d, %dn",t[2*i+2],q);}
q–;//打印表后
}
}
}
return 0;
}