hihocoder #1616 : 是二叉搜索树吗？(模拟题)

题目链接：http://hihocoder.com/problemset/problem/1616

题解：就是简单的模拟一下至于如何判断是不是二叉搜索树可以通过中序遍历将每个点存下来看是不是递增的如果是递增的就是反之不是

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int M = 1e4 + ;
vector<int> vc[M];
int fa[M] , ch[M][] , f[M] , n , emmm , num[M];
void init() {
    for(int i =  ; i <= n ; i++) {
        f[i] = i;
        vc[i].clear();
    }
}
int find(int x) {
    if(x == f[x]) return f[x];
    return f[x] = find(f[x]);
}
int cnt;
void cau(int u) {
    int len = vc[u].size();
    if(len == ) {
        if(vc[u][] == vc[u][] || vc[u][] == u || vc[u][] == u) emmm = ;
        cau(vc[u][]);
        num[cnt++] = u;
        cau(vc[u][]);
    }
    if(len == ) {
        if(vc[u][] == u) emmm = ;
        if(vc[u][] > u) {
            num[cnt++] = u;
            cau(vc[u][]);
        }
        else {
            cau(vc[u][]);
            num[cnt++] = u;
        }
    }
    if(len == ) {
        num[cnt++] = u;
    }
}
void dfs(int u) {
    int len = vc[u].size();
    if(len == ) {
        if(u > vc[u][]) {
            putchar('(');
            printf("%d" , vc[u][]);
            dfs(vc[u][]);
            putchar(')');
            putchar('(');
            putchar(')');
        }
        else {
            putchar('(');
            putchar(')');
            putchar('(');
            printf("%d" , vc[u][]);
            dfs(vc[u][]);
            putchar(')');
        }
    }
    if(len == ) {
        putchar('(');
        printf("%d" , vc[u][]);
        dfs(vc[u][]);
        putchar(')');
        putchar('(');
        printf("%d" , vc[u][]);
        dfs(vc[u][]);
        putchar(')');
    }
    if(len == ) {
        putchar('(');
        putchar(')');
        putchar('(');
        putchar(')');
    }
}
int main() {
    int t;
    scanf("%d" , &t);
    while(t--) {
        cnt = ;
        scanf("%d" , &n);
        memset(fa , - , sizeof(fa));
        int flag = ;
        init();
        for(int i =  ; i <= n -  ; i++) {
            int u , v;
            scanf("%d%d" , &u , &v);
            vc[u].push_back(v);
            int a = find(u) , b = find(v);
            if(a == b) {
                flag = ;
            }
            else {
                f[b] = a;
            }
            if(fa[v] == -) {
                fa[v] = u;
                continue;
            }
            else {
                flag = ;
            }
        }
        if(flag) {
            printf("ERROR1\n");
        }
        else {
            int tmp = ;
            for(int i =  ; i <= n ; i++) {
                if(vc[i].size() == ) continue;
                sort(vc[i].begin() , vc[i].end());
                if(vc[i].size() > ) {
                    tmp = ;
                    break;
                }
            }
            if(tmp) {
                printf("ERROR2\n");
            }
            else {
                emmm = ;
                int root = ;
                for(int i =  ; i <= n ; i++) {
                    if(fa[i] == -) {
                        root = i;
                        break;
                    }
                }
                cau(root);
                for(int i =  ; i < cnt ; i++) {
                    if(num[i] <= num[i - ]) {
                        emmm = ;
                        break;
                    }
                }
                if(emmm) {
                    printf("ERROR3\n");
                }
                else {
                    putchar('(');
                    printf("%d" , root);
                    dfs(root);
                    putchar(')');
                    puts("");
                }
            }

        }
    }
    return ;
}