三角形那个题，直接先判断能不能构成三角形，不行的话，最长边等于两短边和-1就可以了啊 #include <iostream> #include <vector> #include <algorithm> #include <numeric> using namespace std; int main() { vector<int>edges(3); for (int i = 0; i < 3; ++i) { cin >> edges[i]; } sort(edges.begin(), edges.end()); if (edges[1] + edges[0]>edges[2] && edges[2] - edges[0] < edges[1]) { cout << edges[0] + edges[1] + edges[2] << endl; } else { cout << 2 * (edges[0] + edges[1]) - 1 << endl; } return 0; }