1020 中序，后序转换为层序遍历

#include <cstdio>#include <iostream>#include <algorithm>#include <vector>using namespace std;vector<int> post, in, level(100000, -1);//与输出前序类似，根左右，加了个树的下标。void pre(int root, int start, int end, int index) {    if(start > end) return ;    int i = start;    while(i < end && in[i] != post[root]) i++;    level[index] = post[root];    pre(root - 1 - end + i, start, i - 1, 2 * index + 1);    pre(root - 1, i + 1, end, 2 * index + 2);}int main() {    int n, cnt = 0;    scanf("%d", &n);    post.resize(n);    in.resize(n);    for(int i = 0; i < n; i++) scanf("%d", &post[i]);    for(int i = 0; i < n; i++) scanf("%d", &in[i]);    pre(n-1, 0, n-1, 0);    for(int i = 0; i < level.size(); i++) {        if(level[i] != -1) {            printf("%d", level[i]);            cnt++;            if(cnt!=n)                cout<<" ";            else if(cnt==n)                break;        }    }    return 0;}