leetcode(63)不同路径 2

不同路径2

解题思路：动态规划+自底向上+去除障碍

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int xlen = obstacleGrid.length;
        int ylen = obstacleGrid[0].length;
        int min = Math.min(xlen,ylen);
        int max = Math.max(xlen,ylen);
        int[][] flags = new int[2][min];
        boolean minflags = false;
        boolean maxflags = false;
        int cur = 0;
        int sum = 0;
        if(min==xlen){
            for(int i=0;i<xlen+ylen-1;++i){
                sum = 0;
                for(int j=0;j<min;++j){
                    if(i-j>=0&&i-j<max){
                        if(obstacleGrid[j][i-j]==1){
                            flags[cur][j] = 0; 
                            if(j==0&&!minflags){
                                minflags = true;
                            }
                            if(i-j==0&&!maxflags){
                                maxflags = true;
                            }
                        }else{
                            if(j==0||i-j==0){
                                if(j==0&&!minflags||i-j==0&&!maxflags){
                                    flags[cur][j] = 1; 
                                }else{
                                    flags[cur][j] = 0;  
                                }
                            }else{
                                flags[cur][j] = flags[1-cur][j-1] + flags[1-cur][j];
                            }
                        }
                        sum += flags[cur][j];
                    }
                }
                if(sum==0){
                    return 0;
                }
                cur = 1 - cur;
            }
        }else{
            for(int i=0;i<xlen+ylen-1;++i){
                sum = 0;
                for(int j=0;j<min;++j){
                    if(i-j>=0&&i-j<max){
                        if(obstacleGrid[i-j][j]==1){
                            flags[cur][j] = 0; 
                            if(j==0&&!maxflags){
                                maxflags = true;
                            }
                            if(i-j==0&&!minflags){
                                minflags = true;
                            }
                        }else{
                            if(j==0||i-j==0){
                                if(j==0&&!maxflags||i-j==0&&!minflags){
                                    flags[cur][j] = 1; 
                                }else{
                                    flags[cur][j] = 0;  
                                }
                            }else{
                                flags[cur][j] = flags[1-cur][j-1] + flags[1-cur][j];
                            }
                        }
                        sum += flags[cur][j];
                    }
                }
                if(sum==0){
                    return 0;
                }
                cur = 1 - cur;
            }
        } 
        return flags[1-cur][min-1];
    }
}