Leetcode64. 最小路径和

题目传送地址: ​​https://leetcode.cn/problems/minimum-path-sum/​​

运行效率：

代码如下:

public int minPathSum(int[][] grid) {
        //右下角的坐标
        int m = grid.length - 1;
        int n = grid[0].length - 1;
        HashMap<String,Integer> map = new HashMap<>();
        int path = minPath(m, n, grid,map);
        return path;
    }

    public int minPath(int m, int n, int[][] grid, HashMap<String,Integer> map) {
        String key = m + ":" + n;
        if(map.containsKey(key)){
           return map.get(key);
        }
        //处理边界情况
        if (m == 0) {
            int path = grid[0][n];
            while (n > 0) {
                path += grid[0][n - 1];
                n--;
            }
            return path;
        }
        if (n == 0) {
            int path = grid[m][0];
            while (m > 0) {
                path += grid[m-1][0];
                m--;
            }
            return path;
        }
        //走到(m,n)位置有2种走法，第一种是从(m-1,n)到(m,n)  第二种是从(m,n-1)到(m,n)
        int i = minPath(m - 1, n, grid,map);
        int j = minPath(m, n - 1, grid,map);
        int res = Math.min(i, j) + grid[m][n];
        map.put(key,res);
        return res;
    }