• poj 3071 概率dp


    //分析:明显的树形关系,题目描述的是一棵高 n + 1的完全二叉树,则 dp[树层号][team号](规定最底层为 0 层,层数朝节点的方向依次递增),推一下就好了

    //稍微需要想一下的是比赛双方的选取,下面给出两种方法

    //#1 枚举起点划分team区间

     1 #include "iostream"
     2 #include "cstdio"
     3 #include "cstring"
     4 #include "algorithm"
     5 using namespace std;
     6 double dp[10][130], mat[130][130];
     7 int n;
     8 
     9 int main()
    10 {
    11     int i, j, k, t;
    12     while(scanf("%d", &n) && (n != -1)) {
    13         for(i = 1; i <= (1 << n); ++i)
    14             for(j = 1; j <= (1 << n); ++j)
    15                 scanf("%lf", &mat[i][j]);
    16         memset(dp, 0, sizeof(dp));
    17         int tot = 1 << n, half;
    18         for(i = 1; i <= tot; ++i)
    19             dp[0][i] = 1;
    20         for(i = 1; i <= n; ++i) {
    21             tot = 1 << i, half = 1 << (i - 1);
    22             for(j = 1; j <= (1 << n); j += tot) {
    23                 for(k = j; k <= j + half - 1; ++k) {
    24                     for(t = j + half; t <= j + tot - 1; ++t) {
    25                         dp[i][k] += dp[i - 1][k] * dp[i - 1][t] * mat[k][t];
    26                         dp[i][t] += dp[i - 1][k] * dp[i - 1][t] * mat[t][k];
    27                     }
    28                 }
    29             }
    30         }
    31         double ans = 0;
    32         int res = 1;
    33         for(i = 1; i <= (1 << n); ++i)
    34             if(ans < dp[n][i])
    35                 ans = dp[n][i], res = i;
    36         printf("%d
    ", res);
    37     }
    38 }

    //#2 比较向上 i - 1 层的根节点序号(存在提前相遇情况)

     1 #include "iostream"
     2 #include "cstdio"
     3 #include "cstring"
     4 #include "algorithm"
     5 using namespace std;
     6 double dp[10][130], mat[130][130];
     7 int n;
     8 
     9 int main()
    10 {
    11     int i, j, k;
    12     while(scanf("%d", &n) && (n != -1)) {
    13         for(i = 1; i <= (1 << n); ++i)
    14             for(j = 1; j <= (1 << n); ++j)
    15                 scanf("%lf", &mat[i][j]);
    16         memset(dp, 0, sizeof(dp));
    17         for(i = 1; i <= (1 << n); ++i)
    18             dp[0][i] = 1;
    19         for(i = 1; i <= n; ++i) {
    20             for(j = 1; j <= (1 << n); ++j) {
    21                 for(k = 1; k <= (1 << n); ++k) {
    22                     int root_j = (j - 1) >> (i - 1), root_k = (k - 1) >> (i - 1);
    23                     if(root_j != root_k && (root_j >> 1) == (root_k >> 1)) {    //向上 i - 1 层的根节点不同 且 是同一节点的左右孩子
    24                         dp[i][j] += dp[i - 1][j] * dp[i - 1][k] * mat[j][k];
    25                         dp[i][k] += dp[i - 1][j] * dp[i - 1][k] * mat[k][j];
    26                     }
    27                 }
    28             }
    29         }
    30         int res = 1;
    31         double ans = 0;
    32         for(i = 1; i <= (1 << n); ++i)
    33             if(ans < dp[n][i])
    34                 ans = dp[n][i], res = i;
    35         printf("%d
    ", res);
    36     }
    37 }
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  • 原文地址:https://www.cnblogs.com/AC-Phoenix/p/4295396.html
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