记忆化搜索系列一＞不同路径

/**
    记忆化搜索：

     */
    int[][] memo;
    public int uniquePaths(int m, int n) {
        //备忘录：
        memo = new int[m+1][n+1];
        return dfs(m,n);
    }

    private int dfs(int i, int j){
        if(i == 0 || j == 0) return 0;
        if(i == 1 && j == 1) {
            memo[i][j] = 1;
            return 1;
        }

        if(memo[i][j] != 0)
            return memo[i][j];

        memo[i][j] = dfs(i-1,j)+dfs(i,j-1);
        return memo[i][j];