第九届北京化工大学程序设计竞赛网络同步赛

A题：dfs，从打到搜索

#include<iostream>#include<math.h>#include<stdio.h>#include<algorithm>#include<string.h>#include<vector>#include<queue>#include<map>#include<set>#define B(x) (1<<(x))using namespace std;typedef long long ll;typedef unsigned long long ull;const int oo = 0x3f3f3f3f;const ll OO = 0x3f3f3f3f3f3f3f3f;const double eps = 1e-9;#define lson rt<<1#define rson rt<<1|1void cmax(int& a, int b){ if (b>a)a = b; }void cmin(int& a, int b){ if (b<a)a = b; }void cmax(ll& a, ll b){ if (b>a)a = b; }void cmin(ll& a, ll b){ if (b<a)a = b; }void cmax(double& a, double b){ if (a - b < eps) a = b; }void cmin(double& a, double b){ if (b - a < eps) a = b; }void add(int& a, int b, int mod){ a = (a + b) % mod; }void add(ll& a, ll b, ll mod){ a = (a + b) % mod; }const ll MOD = 1000000007;const int maxn = 50;int a[maxn];ll sum[maxn];int f;void dfs(int s, int l){if (f) return;if (l > sum[s]) return;if (l == sum[s] || l == 0){f = 1;return;}for (int i = s; i >= 1; i--){if (l >= a[i])dfs(i - 1, l - a[i]);}}int main(){int n, m;while (scanf("%d %d", &n, &m) != EOF){sum[0] = 0;for (int i = 1; i <= n; i++){scanf("%d", &a[i]);sum[i] = sum[i - 1] + a[i];}f = 0;dfs(n, m);if (f) printf("Yes\n");else printf("No\n");}return 0;}

B题：ac自动机，将前后相减等到的串去匹配，由于有负值，所以用结构体，用map存边。

#include<iostream>#include<math.h>#include<stdio.h>#include<algorithm>#include<string.h>#include<vector>#include<queue>#include<map>#include<set>using namespace std;#define B(x) (1<<(x))typedef long long ll;const int oo = 0x3f3f3f3f;const ll OO = 1LL << 61;const int MOD = 10007;const int maxn = 110000;const int maxm = 1000005;const int SIZE = 1000005;int Next_[maxm];//const int type=4; inline int gcd(int a, int b){    return b == 0 ? a : gcd(b, a%b);} struct Node{    int x;     Node(){}     Node(int a){        x = a;    }     bool operator==(const Node& a)const{         return x == a.x;    }     bool operator!=(const Node& a)const{         return x != a.x;    }     bool operator<(const Node& a)const{        return x < a.x;    } }a[maxn], b[maxn]; void input(Node buff[], int len){     int x, y;    scanf("%d", &x);    for (int i = 1; i<len; i++){         scanf("%d", &y);        buff[i] = Node(y - x);        x = y;    }} map<Node, int>Next[SIZE];int fail[SIZE], flag[SIZE];int cnt, root;  int newNode(){     Next[cnt].clear();    flag[cnt++] = 0;    return cnt - 1;} void Init(){     cnt = 1;    root = newNode();} void Insert(Node buff[], int len){     int now = root;    Node k;    for (int i = 1; i <= len; i++){         k = buff[i];        if (Next[now][k] == 0)            Next[now][k] = newNode();        now = Next[now][k];    }//for    flag[now]++;} void build(){     fail[root] = 0;    Node k;    queue<int>Q;     ///注：next[now][i] <=> it->second ; i <=>it->first;    for (map<Node, int>::iterator it = Next[root].begin(); it != Next[root].end(); ++it){         fail[it->second] = root;        Q.push(it->second);    }//for     while (!Q.empty()){         int now = Q.front(); Q.pop();        flag[now] += flag[fail[now]];        for (map<Node, int>::iterator it = Next[now].begin(); it != Next[now].end(); ++it){             int temp = fail[now];            int nxt = Next[temp][it->first];            while (temp&&!nxt){                 temp = fail[temp];                nxt = Next[temp][it->first];            }            if (temp) fail[it->second] = nxt;            else fail[it->second] = root;            Q.push(it->second);        }//for    }//while} ll Search(Node buff[], int len){     int now = root;    ll ans = 0;    for (int i = 1; i <= len; i++){         int nxt = Next[now][buff[i]];        while (now&&!nxt){             now = fail[now];            nxt = Next[now][buff[i]];        }        if (now) now = nxt;        else now = root;        ans += flag[now];    }//for    return ans;} void get_next(Node T[], int len){    int i = 0;    Next_[i] = -1;    int j = -1;    while (i<len)    {        if (j == -1 || T[i] == T[j]){             i++; j++;            Next_[i] = j;        }        else j = Next_[j];    }} ll kmp(Node S[], Node T[], int lenS, int lenT){     ll ans = 0;    int i = 0, j = 0;    while (i<lenS){         if (j == -1 || S[i] == T[j]){             i++;            j++;        }        else j = Next_[j];        if (j == lenT) ans++;    }//for    return ans;} int main(){     int T, m, n, k;    ll ans;    while (scanf("%d %d", &n, &m) != EOF){         Init();         input(a, n);         ans = 0;        if (m > 1){             for (int i = 1; i <= m; i++){                 scanf("%d", &k);                input(b, k);                if (k > 1) Insert(b, k - 1);                else ans += n;            }             build();            ans += Search(a, n - 1);         }        else{             scanf("%d", &k);            input(b, k);             if (k > 1){                get_next(b + 1, k - 1);                ans = kmp(a + 1, b + 1, n - 1, k - 1);            }            else ans += n;        }        cout << ans << endl;     }    return 0;}

D题：二分图，先判断二分图，然后二分匹配。

#include<iostream>#include<math.h>#include<stdio.h>#include<algorithm>#include<string.h>#include<string>#include<vector>#include<queue>#include<map>#include<set>#define B(x) (1<<(x))using namespace std;typedef long long ll;typedef unsigned long long ull;void cmax(int& a, int b){ if (b>a)a = b; }void cmin(int& a, int b){ if (b<a)a = b; }void cmax(ll& a, ll b){ if (b>a)a = b; }void cmin(ll& a, ll b){ if (b<a)a = b; }void add(int& a, int b, int mod){ a = (a + b) % mod; }void add(ll& a, ll b, ll mod){ a = (a + b) % mod; }#define lson rt<<1#define rson rt<<1|1const int oo = 0x3f3f3f3f;const ll OO = 0x3f3f3f3f3f3f3f3f;const ll MOD = 1000000007;const int maxn = 333;map<string, int> mat;char s1[20], s2[20];int g[maxn][maxn], col[maxn];int mac[maxn], vis[maxn];int n; bool jud(){    queue<int>q;    memset(col, -1, sizeof col);    for (int i = 1; i <= n; i++){        if (col[i] != -1)continue;        col[i] = 1;        q.push(i);        while (!q.empty()){            int u = q.front(); q.pop();            for (int v = 1; v <= n; v++)if (g[u][v]){                if (col[v] == -1){                    col[v] = 1 - col[u];                    q.push(v);                }                else if (col[u] == col[v]) return false;            }        }    }    return true;} int dfs(int u){    for (int i = 1; i <= n; i++){        if (g[u][i] && !vis[i]){            vis[i] = 1;            if (mac[i] == -1 || dfs(mac[i])){                mac[i] = u;                return 1;            }        }    }    return 0;} int Match(){    memset(mac, -1, sizeof mac);    int ans = 0;    for (int i = 1; i <= n; i++){        memset(vis, 0, sizeof vis);        ans += dfs(i);    }    return ans;} int main(){    int m;    while (scanf("%d %d", &n, &m) != EOF){        int cnt = 0;        mat.clear();        memset(g, 0, sizeof g);        for (int i = 1; i <= m; i++){            scanf("%s %s", s1, s2);            if (!mat[s1])mat[s1] = ++cnt;            if (!mat[s2])mat[s2] = ++cnt;            g[mat[s1]][mat[s2]] = 1;            g[mat[s2]][mat[s1]] = 1;        }        if (!jud()) puts("No");        else{            printf("%d\n", Match());        }    }    return 0;}

E题：

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>using namespace std;int a[2][2], b[2][2], c[2][2], g[2];#define exp 1e-6int main(){    int n;    while (~scanf("%d", &n))    {        int x, y, z, m;        a[0][0] = a[1][1] = a[1][0] = a[1][1] = 0;        b[0][0] = b[1][1] = b[1][0] = b[1][1] = 0;        c[0][0] = c[1][1] = c[1][0] = c[1][1] = 0;        g[0] = g[1] = 0;        for (int i = 0; i < n; i++)        {            scanf("%d%d%d%d", &x, &y, &z, &m);            a[m][x]++;            b[m][y]++;            c[m][z]++;            g[m]++;        }        scanf("%d%d%d", &x, &y, &z);        double xx, yy;        xx = (a[0][x] + 1.0 / n)*b[0][y] / n*c[0][z] / n*g[0];        yy = (a[1][x] + 1.0 / n)*b[1][y] / n*c[1][z] / n*g[1];        if (yy - xx > exp)            puts("Come on guys,you can do it!");        else            puts("Poor guys,you can go back to sleep now..");    }}

F题：结论题

G题：TL

H题：ORZ

I：贪心，根据上车的人数从小到大排序，然后从终点站到这往前推，如果出现负值说明这种情况无解。

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;struct node{     int x, y;}a[110000]; bool cmp(node a, node b){    return a.y < b.y;}int main(){    int n;    while (~scanf("%d", &n))    {        for (int i = 0; i < n; i++)            scanf("%d%d", &a[i].x, &a[i].y);        sort(a, a + n, cmp);        long long sum = 0;        bool flag = true;        if (a[0].y != 0)            puts("No");        else        {            for (int i = 0; i < n; i++)            {                sum -= a[i].y;                if (sum < 0)                {                    flag = false;                    break;                }                sum += a[i].x;            }            if (flag)                puts("Yes");            else                puts("No");        }    }}

J题：乱搞

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<math.h>using namespace std;int x[1100000], y[1100000];int main(){    int n;    while (~scanf("%d", &n))    {        for (int i = 0; i < n; i++)            scanf("%d%d", &x[i], &y[i]);        sort(y, y + n);        int k = y[n / 2];        long long sum = 0;        for (int i = 0; i < n; i++)            sum += abs(y[i] - k);        printf("%lld\n", sum);    }}