[leetcode] Unique Paths II

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Unique Paths II

思路：

当前位置为1，走法为0；当前位置为0，走法=当前位置的上边位置的走法+当前位置的左边位置的走法

注意边界的处理

class Solution {public:    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {        int row =obstacleGrid.size();//获取行数        if (row==0) {            return 0;        }        int column=obstacleGrid[0].size();//获取列数                vector<vector<int>> fun(row,vector<int>(column));//开辟相同大小的矩阵，并初始化为0        int i,j;        for (i=0; i<row; ++i) {            for (j=0; j<column; ++j) {                fun[i][j]=0;            }        }        //特殊位置处理        fun[0][0]=(obstacleGrid[0][0]==1?0:1);//fun[0][0]        for (i=1; i<row; ++i) {//第一列,注意i从1开始            fun[i][0]=(obstacleGrid[i][0]==1?0:fun[i-1][0]);        }        for (j=1; j<column; ++j) {//第一行            fun[0][j]=(obstacleGrid[0][j]==1?0:fun[0][j-1]);        }        //从fun[1][1]开始处理        for (i=1; i<row; ++i) {            for (j=1; j<column; ++j) {                fun[i][j]=(obstacleGrid[i][j]==1?0:(fun[i-1][j]+fun[i][j-1]));            }        }        return fun[row-1][column-1];    }};

参考：leetcode unique path II

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

class Solution {public:    //状态定义为从起点--当前节点的走法    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {        if(obstacleGrid.size()==0){            return 0;        }        int sum[obstacleGrid.size()][obstacleGrid[0].size()];        //状态初始化        sum[0][0]=(obstacleGrid[0][0]==0?1:0);        for(int i=1;i<obstacleGrid.size();++i){            sum[i][0]=(obstacleGrid[i][0]==1?0:sum[i-1][0]);        }        for(int j=1;j<obstacleGrid[0].size();++j){            sum[0][j]=(obstacleGrid[0][j]==1?0:sum[0][j-1]);        }        //状态转移        for(int i=1;i<obstacleGrid.size();++i){            for(int j=1;j<obstacleGrid[0].size();++j){                sum[i][j]=(obstacleGrid[i][j]==1?0:(sum[i-1][j]+sum[i][j-1]));            }        }        return sum[obstacleGrid.size()-1][obstacleGrid[0].size()-1];    }};

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