# Concise C++ DFS

• At each level, select two numbers and compute with + - * /, to get every possible answer.
Note that - and / have order, need to compute a - b, b - a, a / b, b / a, four possible branches.

``````class Solution {
public:
bool res = false;
bool judgePoint24(vector<int>& nums) {
vector<float> NUMS(nums.begin(), nums.end());
return helper(NUMS);
}
bool helper(vector<float>& nums){
if(nums.size() == 1){
return abs(24 - nums[0]) < 0.00001;
}
for(int i = 0; i < nums.size(); i ++){
for(int j = i+1; j < nums.size(); j ++){
vector<float> new_nums = nums;
float m = new_nums[i], n = new_nums[j];
new_nums.erase(new_nums.begin() + j);

new_nums[i] = m + n; if(helper(new_nums)) return true;
new_nums[i] = m * n; if(helper(new_nums)) return true;

new_nums[i] = m - n; if(helper(new_nums)) return true;
new_nums[i] = n - m; if(helper(new_nums)) return true;

if(n != 0) {new_nums[i] = m / n; if(helper(new_nums)) return true;}
if(m != 0) {new_nums[i] = n / m; if(helper(new_nums)) return true;}
}
}
return false;
}
};
``````

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