Count Complete Tree Nodes || LeetCode

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
#define MAX 1000
int Path[MAX];
int index1;

int power(int x,int n){
    int i,re;
    if(n==0)return 1;
    for(i=0,re=1;i<n;++i){
        re=re*x;
    }
    return re;
}

void find_path(struct TreeNode *root){
    if( (root->left==NULL&&root->right==NULL) || (root==NULL) )return  ;
    struct TreeNode *t1,*t2;
    t1=root->left,t2=root->right;
    while(t1&&t2){
        t1 = t1->left;
        t2 = t2->left;
    }
    if(t1){
        Path[index1++]=0;
        find_path(root->left);
    }
    else {
        Path[index1++]=1;
        find_path(root->right);
    }
}

int countNodes(struct TreeNode* root) {
    int  nlevel,i,temp,start,end;

    if(root==NULL)return 0;
    if(root->left==NULL && root->right==NULL) return 1;
    index1=0;
    find_path(root);
    nlevel=power(2,index1);
    for(i=0,start=1,end=nlevel;i<index1;++i)
    {
        if(Path[i]==0)
            end=(end+start)/2;
        else
            start=(end+start)/2+1;
        if (end==start)break;
    }
    return nlevel-1+start;
}