Monday, June 16, 2014

Unique Path II -- Leetcode

Question:
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.
Answer:
class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
       
        int m= obstacleGrid.size();
        int n= obstacleGrid[0].size();
        int dp[m][n];
       
            //Initialize the edge cases for the dp table.
        if(obstacleGrid[0][0]==0){
            dp[0][0]=1;
        }else{
            dp[0][0]=0;
        }
       
        for(int i=1;i<m;++i){
            if(obstacleGrid[i][0]==1){
               dp[i][0]=0;
            }
            else{
                dp[i][0]=dp[i-1][0];
            }
        }
        for(int j=1;j<n;++j){
            if(obstacleGrid[0][j]==1){
               dp[0][j]=0;
            }
            else{
               dp[0][j]=dp[0][j-1];
            }
        }
            //Recursion cases for dp table
        for(int i=1; i<m;++i){
            for(int j=1;j<n;++j){
                if(obstacleGrid[i][j]==0){
                   dp[i][j]= dp[i-1][j]+dp[i][j-1];
                }else{
                   dp[i][j]= 0;
                }
            }
        }
        return dp[m-1][n-1];
    }
};

No comments:

Post a Comment