PAT1147heaps-二叉树的后序遍历+vector误区点

先是错误代码，然后改正：

//思路：存入数组，flag判断，后序遍历。

/*
//出现输入一串后再输不进去
#include<bits/stdc++.h>
#define MAXN 1010
using namespace std;

int flag, n;
vector<int> pos;

void postOrder(int now){
    if(now <= (n-1)/2){
        postOrder(now*2);
        postOrder(now*2+1);
    }
    else return;
    if(now == 1)
        cout << pos[now];
    else cout << " " << pos[now];
}

int main(){
    int m;
    cin >> m >> n;
    for(int i = 0; i < m; i++){
        for(int j = 1; j <= n; j++){
            cin >> pos[j];
        }
        flag = pos[1] > pos[2]?1:-1;
        int j;
        for(j = 1; j <= (n-1)/2; j++){
            int left = j*2, right = j*2+1;
            if(flag == 1){
                if(pos[left] > pos[j] || pos[right] > pos[j]){
                    cout << "Not Heap\n";
                    break;
                }
            }else if(flag = -1){
                if(pos[left] < pos[j] || pos[right] < pos[j]){
                    cout << "Not Heap\n";
                    break;
                }
            }
        }
        if(j == (n-1)/2){
            if(flag == 1) cout << "Max Heap\n";
            else cout << "Min Heap\n";
        }
        postOrder(1);
    }
    return 0;
}
*/

//改正：
#include<bits/stdc++.h>
#define MAXN 1010
using namespace std;

int flag, n;
vector<int> pos;

void postOrder(int now){
    if(now > n){
        return ;                //放到下一次递归中处理
    }
    postOrder(now*2);
    postOrder(now*2+1);
    if(now == 1)
        cout << pos[now] << endl;
    else cout<< pos[now] << " "; //注意是后序，因此最后输出第一个元素
}

int main(){
    int m;
    cin >> m >> n;
    //pos.resize(n);             //错因
    for(int i = 0; i < m; i++){
        for(int j = 1; j <= n; j++){
            int num;
            cin >> num;
            pos.push_back(num);
        }
        flag = pos[1] > pos[2]?1:-1;
        int j;
        for(j = 1; j <= (n)/2; j++){
            int left = j*2, right = j*2+1;
            if(right > n) right = left;      //两个测试点不过的原因--->修正然后
            if(flag == 1){
                if(pos[left] > pos[j] || pos[right] > pos[j]){
                    cout << "Not Heap\n";
                    break;
                }
            }else if(flag = -1){
                if(pos[left] < pos[j] || pos[right] < pos[j]){
                    cout << "Not Heap\n";
                    break;
                }
            }
        }
        if(j > n/2){                         //错因：细节的处理要清晰
            if(flag == 1) cout << "Max Heap\n";
            else cout << "Min Heap\n";
        }
        postOrder(1);
    }
    return 0;
}