最小路径和 递归求法

最小路径和

http://bit.ly/2RVNkuQ 
我哭了 
```
class Solution {
 

    // 64. 最小路径和  TL
    public int minPathSum(int[][] grid) {
        int rowLen = grid.length;
        int colLen = grid[rowLen-1].length;
        int[][] memo = new int[rowLen][colLen];
        return routerHelper(rowLen - 1, colLen - 1, grid, memo);
    }

    public int routerHelper(int i, int j, int[][] grid, int[][] memo) {
        if (memo[i][j] > 0) {
            return memo[i][j];
        }
        if (i == 0 && j == 0) {
            return memo[i][j] = grid[0][0];
        }
        if (i == 0) {
            return memo[i][j] = routerHelper(i, j - 1, grid, memo) + grid[i][j];
        }
        if (j == 0) {
            return memo[i][j] = routerHelper(i - 1, j, grid, memo) + grid[i][j];
        }
        return memo[i][j] = Math.min(routerHelper(i - 1, j, grid, memo), routerHelper(i, j - 1, grid, memo)) + grid[i][j];
    }
}
```