[leetcode]24-game

. - 力扣（LeetCode）

class Solution {
public:static constexpr int TARGET = 24;static constexpr double EPSILON = 1e-6;static constexpr int ADD = 0, MULTIPLY = 1, SUBTRACT = 2, DIVIDE = 3;bool judgePoint24(vector<int> &nums) {vector<double> l;for (const int &num : nums) {l.emplace_back(static_cast<double>(num));}return solve(l);}bool solve(vector<double> &l) {if (l.size() == 0) {return false;}if (l.size() == 1) {return fabs(l[0] - TARGET) < EPSILON;}int size = l.size();for (int i = 0; i < size; i++) {for (int j = 0; j < size; j++) {if (i != j) {vector<double> list2 = vector<double>();for (int k = 0; k < size; k++) {if (k != i && k != j) {list2.emplace_back(l[k]);}}for (int k = 0; k < 4; k++) {if (k < 2 && i > j) {continue;}if (k == ADD) {list2.emplace_back(l[i] + l[j]);} else if (k == MULTIPLY) {list2.emplace_back(l[i] * l[j]);} else if (k == SUBTRACT) {list2.emplace_back(l[i] - l[j]);} else if (k == DIVIDE) {if (fabs(l[j]) < EPSILON) {continue;}list2.emplace_back(l[i] / l[j]);}if (solve(list2)) {return true;}list2.pop_back();}}}}return false;}
};