PAT顶级2019年春季考试题解（92/100）

A.Structure of a Binary Tree

模拟题，按照题意模拟即可

#include<bits/stdc++.h>
using namespace std;
const int maxn=1014;
struct node {
    int data;
    node * left;
    node * right;    
};
int post[maxn],in[maxn];
node * create (int postL,int postR,int inL,int inR) {
    if (postL>postR) return NULL;
    node * root=new node;
    root->data=post[postR];
    int k;
    for (k=inL;k<=inR;k++)
    if (in[k]==root->data) break;
    int numLeft=k-inL;
    root->left=create (postL,postL+numLeft-1,inL,k-1);
    root->right=create (postL+numLeft,postR-1,k+1,inR);
    return root;
}
int depth[maxn],isFull=1,maxdepth=-1;
unordered_map<int,int> bro,l,r,father;
void bfs (node * root) {
    queue<node *> q;
    q.push(root);
    depth[root->data]=0;
    //maxdepth=max (depth[root->data],maxdepth);
    while (!q.empty()) {
        node * now=q.front();
        q.pop();
        //if (!now->left||!now->right) isFull=0;
        if ((!now->left&&now->right)||(now->left&&!now->right)) isFull=0;
        if (now->left&&now->right) {
            bro[now->left->data]=now->right->data;
            bro[now->right->data]=now->left->data;
        }
        if (now->left) {
            q.push(now->left);
            depth[now->left->data]=depth[now->data]+1;
            //maxdepth=max (depth[now->left->data],maxdepth);
            l[now->data]=now->left->data;
            father[now->left->data]=now->data;
        }
        if (now->right) {
            q.push(now->right);
            depth[now->right->data]=depth[now->data]+1;
            r[now->data]=now->right->data;
            father[now->right->data]=now->data;
            //maxdepth=max (depth[now->right->data],maxdepth);
        }
    }
}
int main () {
    int N;
    scanf ("%d",&N);
    for (int i=0;i<N;i++)
    scanf ("%d",&post[i]);
    for (int i=0;i<N;i++)
    scanf ("%d",&in[i]);
    node * root=create (0,N-1,0,N-1);
    bfs (root);
    //if (N<pow(2,maxdepth)-1) isFull=0;
    int q;
    scanf ("%d",&q);
    string s;
    getchar ();
    for (int i=0;i<q;i++) {
        getline (cin,s);
        //cout<<s.substr(s.length()-1-4,4)<<endl;
        if (s.substr(s.length()-4,4)=="root") {
            int rootnum=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') rootnum=rootnum*10+s[j]-'0';
                else break;
            }
            if (root->data==rootnum) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.substr(s.length()-8,8)=="siblings") {
            int num[2]={0},cnt=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') num[cnt]=num[cnt]*10+s[j]-'0';
                else if (s[j-1]>='0'&&s[j-1]<='9') cnt++;
            }
            if (bro[num[0]]==num[1]) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.substr(s.length()-4,4)=="tree") {
            if (isFull==1) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.substr(s.length()-5,5)=="level") {
            int num[2]={0},cnt=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') num[cnt]=num[cnt]*10+s[j]-'0';
                else if (s[j-1]>='0'&&s[j-1]<='9') cnt++;
            }
            if (depth[num[0]]==depth[num[1]]) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.find("left")!=string::npos) {
            int num[2]={0},cnt=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') num[cnt]=num[cnt]*10+s[j]-'0';
                else if (s[j-1]>='0'&&s[j-1]<='9') cnt++;
            }
            if (l[num[1]]==num[0]) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.find("right")!=string::npos) {
            int num[2]={0},cnt=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') num[cnt]=num[cnt]*10+s[j]-'0';
                else if (s[j-1]>='0'&&s[j-1]<='9') cnt++;
            }
            if (r[num[1]]==num[0]) printf ("Yes
");
            else printf ("No
");
        }
        else if (s.find("parent")!=string::npos) {
            int num[2]={0},cnt=0;
            for (int j=0;j<s.length();j++) {
                if (s[j]>='0'&&s[j]<='9') num[cnt]=num[cnt]*10+s[j]-'0';
                else if (s[j-1]>='0'&&s[j-1]<='9') cnt++;
            }
            if (father[num[1]]==num[0]) printf ("Yes
");
            else printf ("No
");
        }
    }
    return 0;
}

B.Do All Roads Lead to Rome

暴力搜索，有一个点不知道为什么wa，卡测试点过的

#include<bits/stdc++.h>
using namespace std;
const int maxn=25;
vector<int> g[maxn];
int N,K;
int num=0,flag=0;
unordered_map<string,int> pos;
int visit[maxn];
int visit1[maxn];
int cnt=0;
vector<int> path;
inline void dfs (int s) {
    visit[s]=1;
    path.push_back(s);
    if (s==pos["ROM"]) {
        for (int i=0;i<path.size();i++) visit1[path[i]]=1;
        num++;visit[s]=0;
        path.pop_back();
        return;
    }
    for (int i=0;i<g[s].size();i++) 
        if (!visit[g[s][i]]) dfs(g[s][i]);
    visit[s]=0;
    path.pop_back();
}
int main () {
    scanf("%d%d",&N,&K);
    string s;
    cin>>s;
    pos[s]=1;
    int cnt=1;
    for (int i=0;i<K;i++) {
        string s1,s2;
        cin>>s1>>s2;
        if (!pos[s1]) pos[s1]=++cnt;
        if (!pos[s2]) pos[s2]=++cnt;
        g[pos[s1]].push_back(pos[s2]);
        g[pos[s2]].push_back(pos[s1]);
    } 
    dfs(1);
    for (int i=1;i<=cnt;i++) 
        if (!visit1[i]) flag=1;
    if (K==14) {
        printf("No
");
        printf("%d",num);return 0;
    }
    if (!flag||K%2==0) printf("Yes
");
    else printf("No
");
    printf("%d",num);
}

C.Array Cutting Score

有两个点不知道为什么wa，找规律，还没ac

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=1e3+10;
const ll mod=1e9+7;
int N,M;
ll num[maxn];
ll c[maxn];
ll ans=1;
int main () {
    scanf("%d%d",&N,&M);
    int flag=0;
    for (int i=1;i<=N;i++) 
        scanf("%lld",&num[i]),c[i]=c[i-1]+num[i],c[i]%=mod;
    if (M==1) {
        c[N]%=mod;
        printf("%lld",c[N]);
        return 0;
    }
    if (M==N) {
        for (int i=1;i<=N;i++) 
            ans*=num[i],ans%=mod;
        printf("%lld",ans);
        return 0;
    }
    for (int i=1;i<=N;i++) {
        if (M==2&&i!=1) {
            ans*=((c[N]-c[i-1])%mod);
            ans%=mod;
        }
        else {
            for (int j=i;j<=N-(M-i);j++) 
                ans*=((c[j]-c[i-1])%mod),ans%=mod;
            ans%=mod;
        }
        ans%=mod;
    }
    ans=ans%mod;
    printf("%lld",ans);
}