p114 路径数量（含障碍物）(leetcode 63)

Posted 2021-03-01 repinkply

一：解题思路

方法一：Time:O(m*n),Space:O(m*n)

方法二：Time:O(m*n),Space:O(1)

二：完整代码示例 (C++版和Java版)

方法一C++:

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid)
    {
        int m = obstacleGrid.size(), n = obstacleGrid[0].size();
        vector<vector<int>> d(m, vector<int>(n));
        d[0][0] = obstacleGrid[0][0] == 1 ? 0 : 1;
        for (int j = 1; j < n; j++)
            d[0][j] = obstacleGrid[0][j] == 1 ? 0 : d[0][j - 1];
        for (int i = 1; i < m; i++)
            d[i][0] = obstacleGrid[i][0] == 1 ? 0 : d[i - 1][0];

        for (int i = 1; i < m; i++)
            for (int j = 1; j < n; j++)
                d[i][j] = obstacleGrid[i][j] == 1 ? 0 :((long)d[i - 1][j] + (long)d[i][j - 1]);

        return d[m - 1][n - 1];
    }
};

方法一Java:

class Solution {
        public int uniquePathsWithObstacles(int[][] obstacleGrid)
        {
              int m=obstacleGrid.length,n=obstacleGrid[0].length;
              int[][] d=new int[m][n];
              d[0][0]=obstacleGrid[0][0]==1?0:1;
              for(int j=1;j<n;j++)
                  d[0][j]=obstacleGrid[0][j]==1?0:d[0][j-1];
              for(int i=1;i<m;i++)
                  d[i][0]=obstacleGrid[i][0]==1?0:d[i-1][0];

              for(int i=1;i<m;i++)
              {
                  for(int j=1;j<n;j++)
                  {
                      d[i][j]=obstacleGrid[i][j]==1?0:d[i-1][j]+d[i][j-1];
                  }
              }

              return d[m-1][n-1];
        }
    }

方法二C++:

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid)
    {
        int m = obstacleGrid.size(), n = obstacleGrid[0].size();
        vector<int> d(n,0);
        d[0] = obstacleGrid[0][0] == 1 ? 0 : 1;
        for (int i = 0; i < m; i++)
        {
            d[0] = obstacleGrid[i][0] == 1 ? 0 : d[0];
            for (int j = 1; j < n; j++)
                d[j] = obstacleGrid[i][j] == 1 ? 0 : (long)d[j] + (long)d[j-1];
        }

        return d[n-1];
    }
};

方法二Java:

class Solution {
        public int uniquePathsWithObstacles(int[][] obstacleGrid)
        {
              int m=obstacleGrid.length,n=obstacleGrid[0].length;
              int[] d=new int[n];
              d[0]=obstacleGrid[0][0]==1?0:1;
              for(int i=0;i<m;i++)
              {
                  d[0]=obstacleGrid[i][0]==1?0:d[0];
                  for(int j=1;j<n;j++)
                      d[j]=obstacleGrid[i][j]==1?0:d[j]+d[j-1];
              }

              return d[n-1];
        }
    }