【 2013 Multi-University Training Contest 5 】

HDU 4647 Another Graph Game

如果没有边的作用，显然轮流拿当前的最大值即可。

加上边的作用，将边权平均分给两个点，如果一个人选走一条边的两个点，就获得了边的权值；如果分别被两个人拿走，两人的差值不变。

将边权平均分配给点，对点的权值排序轮流选择。

 #include<cstdio>
 #include<algorithm>
 #include<iostream>
 #define MAXN 100010
 #define EPS 1e-8
 typedef long long LL;
 using namespace std;
 double arr[MAXN];
 int main() {
     int n, m;
     int i;
     int x, y, val;
     double a, b;
     while (~scanf("%d%d", &n, &m)) {
         for (i = ; i <= n; i++) {
             scanf("%lf", &arr[i]);
         }
         for (i = ; i < m; i++) {
             scanf("%d%d%d", &x, &y, &val);
             arr[x] += val * 0.5 + EPS;
             arr[y] += val * 0.5 + EPS;
         }
         sort(arr + , arr +  + n);
         a = b = ;
         for (i = n; i > ; i -= ) {
             a += arr[i];
             b += arr[i - ];
         }
         cout << (LL) (a - b + EPS) << endl;
     }
     return ;
 }

---

HDU 4648 Magic Pen 6

求前缀和，枚举擦除的起点，求出最右端的位置，更新答案。

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define MAXN 100010
 using namespace std;
 int arr[MAXN];
 int sum[MAXN];
 int pos[MAXN];
 int main() {
     int n, m;
     int i;
     int ans;
     while (~scanf("%d%d", &n, &m)) {
         sum[] = ;
         memset(pos, -, sizeof(pos));
         for (i = ; i <= n; i++) {
             scanf("%d", &arr[i]);
             arr[i] = (arr[i] % m + m) % m;
             sum[i] = (sum[i - ] + arr[i]) % m;
             pos[sum[i]] = i;
         }
         ans = ;
         for (i = ; i <= n; i++) {
             ans = max(ans, pos[sum[i - ]] - i + );
         }
         printf("%d\n", ans);
     }
     return ;
 }

---

HDU 4649 Professor Tian

dp[i][j][k]表示第i位，处理到第j个数，该位的结果为k的概率。

答案就是每一位的dp[i][n][1]*(1<<i)相加。

 #include<cstdio>
 #include<cstring>
 #define MAXN 220
 #define MAXM 20
 double dp[MAXM][MAXN][];
 int arr[MAXN];
 char str[MAXN];
 double p[MAXN];
 int main() {
     int n;
     int ca = ;
     int i, j, k, l;
     int tmp;
     double ans;
     while (~scanf("%d", &n)) {
         for (i = ; i <= n; i++) {
             scanf("%d", &arr[i]);
         }
         for (i = ; i <= n; i++) {
             scanf(" %c", &str[i]);
         }
         for (i = ; i <= n; i++) {
             scanf("%lf", &p[i]);
         }
         memset(dp, , sizeof(dp));
         for (i = ; i < MAXM; i++) {
             if (arr[] & ( << i)) {
                 dp[i][][] = ;
             } else {
                 dp[i][][] = ;
             }
             for (j = ; j <= n; j++) {
                 if (arr[j] & ( << i)) {
                     l = ;
                 } else {
                     l = ;
                 }
                 for (k = ; k < ; k++) {
                     if (str[j] == '&') {
                         tmp = k & l;
                     } else if (str[j] == '|') {
                         tmp = k | l;
                     } else {
                         tmp = k ^ l;
                     }
                     dp[i][j][tmp] += dp[i][j - ][k] * ( - p[j]);
                     dp[i][j][k] += dp[i][j - ][k] * p[j];
                 }
             }
         }
         ans = ;
         for (i = ; i < MAXM; i++) {
             ans += dp[i][n][] * ( << i);
         }
         printf("Case %d:\n%lf\n", ca++, ans);
     }
     return ;
 }