Leetcode63. 不同路径 II

题目传送地址：​​https://leetcode.cn/problems/unique-paths-ii/​​

运行效率：

代码如下：

public static int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length-1;
        int n = obstacleGrid[0].length-1;
        return uniquePaths(m, n, obstacleGrid);

    }

    public static int uniquePaths(int m, int n, int[][] obstacleGrid) {
        HashMap<String, Integer> map = new HashMap<>();
        return uniqPathsWithMap(m, n, obstacleGrid, map);
    }

    public static int uniqPathsWithMap(int m, int n, int[][] obstacleGrid, HashMap<String, Integer> map) {
        if (obstacleGrid[m][n] == 1) {
            return 0;
        }
        String key = m + ":" + n;
        if (map.containsKey(key)) {
            return map.get(key);
        }
        //处理边界情况
        if (m == 0) {
            while (n>0){
                if(obstacleGrid[0][n-1]==1){
                    return 0;
                }
                n--;
            }
            return 1;
        }
        if(n==0){
            while (m>0){
                if(obstacleGrid[m-1][0]==1){
                    return 0;
                }
                m--;
            }
            return 1;
        }
        //要想走到(m,n)位置坐标，有2种可能，第一种是从(m-1,n)到(m,n)，  第2种是从(m,n-1)到(m,n)
        int i = uniqPathsWithMap(m - 1, n, obstacleGrid, map) + uniqPathsWithMap(m, n - 1, obstacleGrid, map);
        map.put(m + ":" + n, i);
        return i;
    }