题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1015
这都能过……
1 #include <algorithm> 2 #include <iostream> 3 #include <iomanip> 4 #include <cstring> 5 #include <climits> 6 #include <complex> 7 #include <fstream> 8 #include <cassert> 9 #include <cstdio> 10 #include <bitset> 11 #include <vector> 12 #include <deque> 13 #include <queue> 14 #include <stack> 15 #include <ctime> 16 #include <set> 17 #include <map> 18 #include <cmath> 19 20 using namespace std; 21 22 typedef long long ll; 23 const ll maxn = 15; 24 ll aim; 25 ll n; 26 char str[maxn]; 27 char ans[maxn]; 28 char wtf[maxn]; 29 bool flag; 30 31 ll quickmul(ll x, ll n) { 32 ll ans = 1; 33 ll t = x; 34 while(n) { 35 if(n & 1) { 36 ans = (ans * t); 37 } 38 t = t * t; 39 n >>= 1; 40 } 41 return ans; 42 } 43 44 int main() { 45 // freopen("in", "r", stdin); 46 // freopen("out", "w", stdout); 47 while(~scanf("%I64d %s", &aim, str)) { 48 if(aim == 0 && strcmp("END", str) == 0) break; 49 memset(wtf, 0, sizeof(wtf)); 50 n = strlen(str); 51 ll nn = 1 << n; 52 flag = 0; 53 sort(str, str+n, greater<char>()); 54 for(ll i = 1; i < nn; i++) { 55 ll cnt = 0; 56 memset(ans, 0, sizeof(ans)); 57 for(ll j = 0; j < n; j++) { 58 if((1 << j) & i) { 59 ans[cnt++] = str[j]; 60 } 61 } 62 if(cnt != 5) continue; 63 sort(ans, ans+cnt); 64 do { 65 ll tmp = ans[0] - 'A' + 1; 66 for(ll k = 1; k < cnt; k++) { 67 tmp += quickmul(-1, k) * quickmul(ans[k]-'A'+1, k+1); 68 } 69 if(tmp == aim) { 70 flag = 1; 71 if(strcmp(wtf, ans) < 0) { 72 strcpy(wtf, ans); 73 } 74 } 75 }while(next_permutation(ans, ans+cnt)); 76 } 77 if(!flag) printf("no solution "); 78 else printf("%s ", wtf); 79 } 80 return 0; 81 }