第二种方法：首先分析题意，可用概率的方法来计算，做了好几道百度的题目，觉得大多数是再考概率论，所以首先要弄懂题意，最后做题前把公式写出来，这样编码时才能游刃有余。
本题中下面的第一种用迭代枚举的方法来做是不对的，仅做错误示范
// ConsoleApplication3.cpp : 定义控制台应用程序的入口点。
//
#include<iostream>
#include<vector>
#include<iomanip>
using namespace std;
int main()
{
int M, N, K;
while (cin >> N >> M >> K)
{
vector<vector<int>> lawn(N, vector<int>(M, 0));
vector<vector<float>> pVec(N, vector<float>(M, 0));
pVec[0][0] = 1;
for (int i = 0; i < K; i++)
{
int x, y;
cin >> x >> y;
lawn[x - 1][y - 1] = 1;
}
pVec[0][0] = 1;
for (int x = 0; x < N; x++)
{
for (int y = 0; y < M; y++)
{
if (x == 0 && y == 0)
{
// cout << "x:" << x << "y：" << y << " " << "初始化" << endl;
pVec[0][0] = 1.0;
}
else if (lawn[x][y] == 1)//中间有障碍物
{
// cout << "x:" << x << "y：" << y << "有障碍 " << endl;
pVec[x][y] = 0;
}
else if (x < lawn.size() - 1 && y < lawn[0].size() - 1) //中间
{
// cout <<"x:"<<x<<" y："<<y<<" " <<"中间" << endl;
if (x - 1 >= 0)
{
// cout << "#####" << endl;
pVec[x][y] = pVec[x][y] + pVec[x - 1][y] * 0.5;
// cout << "x-1:" << x-1 << " y：" << y << " " << pVec[x-1][y] << endl;
// cout << "x:" << x << " y：" << y << " " << pVec[x][y] << endl;
}
if (y - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x][y - 1] * 0.5;
}
}
else if (x < lawn.size() - 1 && y == lawn[0].size() - 1) //最右面
{
// cout << "x:" << x << "y：" << y << " " << "最右面" << endl;
if (x - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x - 1][y] * 1;
}
if (y - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x][y - 1] * 0.5;
}
}
else if (x == lawn.size() - 1 && y < lawn[0].size() - 1) //最下面
{
// cout << "x:" << x << "y：" << y << " " << "最下面" << endl;
if (x - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x - 1][y] * 0.5;
}
if (y - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x][y - 1] * 1;
}
}
else //右下角
{
// cout << "x:" << x << "y：" << y << " " << "右下角" << endl;
if (x - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x - 1][y] * 1;
}
if (y - 1 >= 0)
{
pVec[x][y] = pVec[x][y] + pVec[x][y - 1] * 1;
//cout << "下面" << endl;
}
}
}
}
/*for (int i = 0; i < pVec.size(); i++)
{
for (int j = 0; j < pVec[0].size(); j++)
{
cout << pVec[i][j] << " ";
}
}*/
// cout << endl;
cout << setiosflags(ios::fixed);
cout << setprecision(2)<<pVec[N-1][M-1] << endl;
}
return 0;
}
第一种方法：迭代，枚举每条路径，但是当n或m大于10时算法就很慢了，这种方法不适用。当数大于等于9时，考虑使用第二种方法，和这个题目类似的是，京东出的题，小东发年终奖，但是那个题目是在6*6的棋盘上，不用担心算法复杂度，对这个题目不适合。。。。。。。
#include "stdafx.h"
#include<iostream>
#include<vector>
#include<iomanip>
using namespace std;
class Solution {
public:
//没有障碍
int noObstacle(vector<vector<int>> lawn)
{
if (lawn.size() == 1)
{
return 1;
}
else if (lawn[0].size() == 1)
{
return 1;
}
else
{
return deleteRow(lawn) + deleteCol(lawn);
}
}
int deleteRow(vector<vector<int>> lawn)
{
lawn.erase(lawn.begin());
return noObstacle(lawn);
}
int deleteCol(vector<vector<int>> lawn)
{
for (int i = 0; i < lawn.size(); i++)
{
lawn[i].erase(lawn[i].begin());
}
return noObstacle(lawn);
}
//有障碍
int hasObstacle(vector<vector<int>> lawn)
{
if (lawn.size() == 1)
{
bool flag = false;
for (int i = 0; i < lawn[0].size(); i++)
{
if (lawn[0][i] != 0)
{
flag = true;
break;
}
}
if (flag == false) return 0;
return 1;
}
else if (lawn[0].size() == 1)
{
bool flag = false;
for (int i = 0; i < lawn.size(); i++)
{
if (lawn[i][0] != 0)
{
flag = true;
break;
}
}
if (flag == false) return 0;
return 1;
}
else
{
return deleteRow2(lawn) + deleteCol2(lawn);
}
}
int deleteRow2(vector<vector<int>> lawn)
{
if (lawn[1][0] != 0)
{
lawn.erase(lawn.begin());
return noObstacle(lawn);
return 0;
}
else
{
lawn.erase(lawn.begin());
return hasObstacle(lawn);
}
}
int deleteCol2(vector<vector<int>> lawn)
{
if (lawn[0][1] != 0)
{
for (int i = 0; i < lawn.size(); i++)
{
lawn[i].erase(lawn[i].begin());
}
return noObstacle(lawn);
return 0;
}
else
{
for (int i = 0; i < lawn.size(); i++)
{
lawn[i].erase(lawn[i].begin());
}
return hasObstacle(lawn);
}
}
};
int main()
{
int M, N, K;
Solution so;
while (cin>>N>>M>>K)
{
vector<vector<int>> lawn;
for (int i = 0; i < N; i++)
{
vector<int> vec;
for (int j = 0; j < M; j++)
{
vec.push_back(0);
}
lawn.push_back(vec);
}
for (int i = 0; i < K; i++)
{
int x,y;
cin >> x >> y;
lawn[x - 1][y - 1]= lawn[x - 1][y - 1]+1;
}
cout << setiosflags(ios::fixed);
cout << "有障碍：" << so.hasObstacle(lawn)<<endl;
cout << "无障碍：" << so.noObstacle(lawn) << endl;
float p = 1- ((float)so.hasObstacle(lawn)) / ((float)so.noObstacle(lawn));
cout << setprecision(2)<< p << endl;
}
return 0;
}