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class Solution {
public:
    TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if(inorder.size() <= 0 || postorder.size() <= 0)
            return NULL;
        TreeNode * root = buildTreeStep(inorder,0,inorder.size()-1,postorder,0,postorder.size()-1);
        return root;
    }
private:
    TreeNode *buildTreeStep(vector<int> &inorder,int ina,int inb,vector<int>&postorder,int poa,int pob) {
        if(ina > inb || poa > pob)
            return NULL;
        int root = postorder[pob];
        int i;
        for(i = ina;i <= inb;i++) {
            if(inorder[i] == root)break;
        }
        //inleft: ina i-1
        //inright:i+1 inb
        //poleft:poa,(i-1) - ina + poa
        //poright:(i-1) - ina + poa + 1,pob-1
        TreeNode * node = new TreeNode(root);
        node->left = buildTreeStep(inorder,ina,i-1,postorder,poa,(i-1)-ina+poa);
        node->right = buildTreeStep(inorder,i+1,inb,postorder,(i-1) - ina+poa+1,pob-1);
        return node;<br />
    }
};