#include <iostream>

 //#include <fstream>

 #include <iomanip>

 #include <cstdio>

 #include <algorithm>

 #include <cstring>

 using namespace std;

 const int maxn =  *  + ;

 const int space =  * ;

 int main()

 {

     //ofstream out("out.txt");

     int m, n, kase = , volume;    //降水总量

     double eleva[maxn], height;    //每个格子的海拔高度, 输入的高度

     double percnt = ;             //有多少百分比的区域

     while (cin >> m >> n)

     {

         memset(eleva, , sizeof(eleva));

         if (!m && !n) break;

         for (int i = ; i < m; i++)

         {

             for (int j = ; j < n; j++)

             {

                 cin >> height;

                 eleva[i * n + j] = height;

             }

         }

         cin >> volume;

         sort(eleva, eleva + m*n);              //排序

         int k, comput = ;                     //计算已经淹没地区的水量

         for (k = ; k < m*n; k++)

         {

             int tmp = comput + (eleva[k] - eleva[k - ]) * space * k;

             if (tmp >= volume)

                 break;

             comput = tmp;

         }

         double water = (volume - comput) / (double)(k * space) + eleva[k - ];    //最终水平面高度是 = 当前被淹没的最高海拔 + 水面比当前海拔高出的高度

         cout << "Region " << ++kase << "\n";

         cout << fixed << setprecision()

              << "Water level is " << water << " meters.\n";

         double total = m*n;

         percnt = (k*100.0 / total) ;         //被淹没区域比例 = 当前比水平面低的海拔数 / 区域总数

         cout << fixed << setprecision()

             << percnt << " percent of the region is under water.\n\n";

     }

     return ;

 }

如图，将海拔按高矮排序好(先排序好，比较容易计算已经淹没地区的水量),由于是水往地处流，如果水量如图，淹没区域如图中阴影地区。