题目描述

Follow up for “Unique Paths”:

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and empty space is marked as 1 and 0 respectively in the grid.

For example, There is one obstacle in the middle of a 3x3 grid as illustrated below.

[
  [0,0,0],
  [0,1,0],
  [0,0,0]
]

The total number of unique paths is 2.

Note: m and n will be at most 100.

紧跟着上一题Unique Paths, 这一题增加了条件, 在地图上会出现障碍物(用1表示), 障碍物不能出现在路线上. 仍然采用上一题的动态规划法, 只不过多了一条:

  • 所有障碍物的位置到达的路线数量都为0

    class Solution { public: int uniquePathsWithObstacles(vector<vector>& obstacleGrid) { int m = obstacleGrid.size(); if(m == 0) return 0; int n = obstacleGrid[0].size(); vector<vector> arr(m, vector(n, 0)); int i, j; for(i = 0; i < m && obstacleGrid[i][0] != 1; i++) arr[i][0] = 1; for(i = 0; i < n && obstacleGrid[0][i] != 1; i++) arr[0][i] = 1; for(i = 1; i < m; i++){ for(j = 1; j < n; j++){ if(obstacleGrid[i][j]) continue;

                  arr[i][j] = arr[i - 1][j] + arr[i][j - 1];
          }
      }
      
      return arr[m - 1][n - 1];
  }

    };