思路：
完全背包，记录路径。
实现：
1 #include <bits/stdc++.h> 2 using namespace std; 3 const int INF = 0x3f3f3f3f; 4 int v[4] = {1, 5, 10, 25}; 5 int c[4], m; 6 int dp[10005], used[10005], path[10005]; 7 int main() 8 { 9 while (cin >> m >> c[0] >> c[1] >> c[2] >> c[3], m || c[0] || c[1] || c[2] || c[3]) 10 { 11 memset(used, 0, sizeof used); 12 memset(path, 0, sizeof path); 13 path[0] = -1; 14 for (int i = 0; i <= m; i++) dp[i] = -INF; 15 dp[0] = 0; 16 for (int i = 0; i < 4; i++) 17 { 18 memset(used, 0, sizeof used); 19 for (int j = v[i]; j <= m; j++) 20 { 21 if (dp[j - v[i]] != -INF && dp[j - v[i]] + 1 > dp[j] && used[j - v[i]] < c[i]) 22 { 23 dp[j] = dp[j - v[i]] + 1; 24 used[j] = used[j - v[i]] + 1; 25 path[j] = j - v[i]; 26 } 27 } 28 } 29 if (dp[m] <= -INF) { cout << "Charlie cannot buy coffee." << endl; } 30 else 31 { 32 int ans[26]; memset(ans, 0, sizeof ans); 33 while (path[m] != -1) 34 { 35 ans[m - path[m]]++; 36 m = path[m]; 37 } 38 cout << "Throw in " << ans[v[0]] << " cents, " << ans[v[1]] << " nickels, " << ans[v[2]] << " dimes, and " << ans[v[3]] << " quarters." << endl; 39 } 40 } 41 return 0; 42 }