[Swust OJ 666]--初来乍到(题号都这么溜~~，递归，找规律)

 1 #include<iostream>
 2 using namespace std;
 3 char key[20], X[] = " IXCMVLD";//数的五倍用i+4表示
 4 int cnt;
 5 void Rserve(int x){
 6     int i, cur = 0, k = 0, lp = 1;
 7     while (x > cur){
 8         cur = 10 * cur + 9;
 9         k++;
10     }
11     for (i = 1; i < k; i++, lp *= 10);
12     if (x <= 4 * lp - 1){
13         for (i = 0; i < x / lp; i++)
14             key[cnt++] = X[k];
15     }
16     else if (x <= 5 * lp - 1){
17         key[cnt++] = X[k];
18         key[cnt++] = X[k + 4];
19     }
20     else if (x <= 9 * lp - 1){
21         key[cnt++] = X[k + 4];
22         for (i = 0; i < x / lp - 5; i++)
23             key[cnt++] = X[k];
24     }
25     else{
26         key[cnt++] = X[k];
27         key[cnt++] = X[k + 1];
28     }
29     if (x%lp) Rserve(x%lp);
30 }
31 int main(){
32     int i, x;
33     while (cin >> x){
34         cnt = 0;
35         Rserve(x);
36         cout << x << ‘=‘;
37         for (i = 0; i < cnt; i++)
38             cout << key[i];
39         cout << endl;
40     }
41     return 0;
42 }

 1 #include <iostream>
 2 #include <string>
 3 using namespace std;
 4 int x[] = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };
 5 string L[] = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
 6 string exchange(int n){
 7     string s;
 8     int i = 0;
 9     while (n){
10         if (n >= x[i]){
11             n -= x[i];
12             s += L[i];
13         }
14         else
15             i++;
16     }
17     return s;
18 }
19 int main(){
20     int n;
21     while (cin >> n){
22         cout << n << ‘=‘;
23         cout << exchange(n) << endl;
24     }
25     return 0;
26 }