1104. Path In Zigzag Labelled Binary Tree

class Solution {
public:
    // this is math problem
    // [1] [3,2] [4,5,6,7] [15,14,13,12,11,10,9,8]
    // 14 -> [4-th 14-8+1=7 nodes ->  3-th ceil(7/2)=4 nodes, 8-4=4]->3-th row
    // 4 -> [3-th, 4-4+1=1; ceil]
    vector<int> pathInZigZagTree(int label) {
        int row = floor(log(label)/log(2))+1; //1 层
        cout<<row<<endl; //4
        vector<int> res(row, 0); // [0]
        res[row-1] = label; // [1]
        res[0] = 1; // [1]
        for(int j=row-2;j>=0;j--){ //j=2:1,0
            // j=2: 8-3=5
            res[j] = pow(2, j+1) - ceil((res[j+1]-pow(2, j+1)+1)/2.0);
        }
        return res;
    }
};