梦幻泡影oO：1. 排列小球（C++，67%，TLE） #include <iostream> #include <vector> using namespace std; int bs[3]; int n; int ans; vector<int> tmp; void dfs(int step) { if (tmp.size() == n) { ans += 1; return; } for (int i = 0; i < 3; i++) { if (bs[i] > 0 && i != tmp.back()) { tmp.push_back(i); bs[i] -= 1; dfs(step + 1); bs[i] += 1; tmp.pop_back(); } } } void solve() { cin >> bs[0] >> bs[1] >> bs[2]; n = bs[0] + bs[1] + bs[2]; ans = 0; for (int i = 0; i < 3; i++) { if (bs[i] > 0) { tmp.push_back(i); bs[i] -= 1; dfs(1); bs[i] += 1; tmp.pop_back(); } } cout << ans; } int main() { solve(); //cout << endl; //system("PAUSE"); return 0; }