标签：style blog color os io for ar div cti
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.
思路：path[i][j]表示从(0,0)到达(i-1,j-1)的不同路径数。则，(i-1,j-1)可以由(i-2,j-1)或者(i-1,j-2)达到，这两种是完全不同的走法。因此，若obstacleGrid[i-1][j-1] == 1，则path[i][j] = path[i-1][j] + path[i][j-1]；否则，path[i][j] = 0。
1 class Solution { 2 public: 3 int uniquePathsWithObstacles( vector<vector<int>> &obstacleGrid ) { 4 if( obstacleGrid.empty() || obstacleGrid[0].empty() ) { return 0; } 5 int rows = obstacleGrid.size(), cols = obstacleGrid[0].size(); 6 vector<vector<int>> path( rows+1, vector<int>( cols+1, 0 ) ); 7 path[1][0] = 1; 8 for( int i = 1; i <= rows; ++i ) { 9 for( int j = 1; j <= cols; ++j ) { 10 if( obstacleGrid[i-1][j-1] == 1 ) { 11 path[i][j] = 0; 12 } else { 13 path[i][j] = path[i-1][j] + path[i][j-1]; 14 } 15 } 16 } 17 return path.back().back(); 18 } 19 };
标签：style blog color os io for ar div cti
原文地址：http://www.cnblogs.com/moderate-fish/p/3935605.html
