UVA 10821 - Constructing BST(贪心构造)

UVA 10821 - Constructing BST

题目链接

题意：有1 - n的数字，要构造一棵高度不超过h的BST，并且要字典序最小的，输出序列

思路：贪心构造，既然字典序最小，那么每个子树的根都要尽量小，那么也就是右子树尽量填满，按照这个策略去dfs构造即可

代码：

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;int n, h;void dfs(int s, int n, int h) {    if (h == 0 || n == 0) return;    int tmp = max(0, n - (1<<(h - 1)));    printf(" %d", s + tmp + 1);    dfs(s, tmp, h - 1);    dfs(s + tmp + 1, n - tmp - 1, h - 1);}int main() {    int cas = 0;    while (~scanf("%d%d", &n, &h) && n || h) {printf("Case %d:", ++cas);if ((1<<h) - 1 < n) {    printf(" Impossible.\n");    continue;}dfs(0, n, h);printf("\n");    }    return 0;}