代码随想录训练营第38天|62.不同路径，63.不同路径II

62.不同路径

文章

代码随想录|0062.不同路径

思路

$$\begin{array}{c}dp[i][j]=\{\begin{array}{rlr}1& ,& i=0\wedge j=0\\ dp[i-1][j]+dp[i][j-1]& ,& else\end{array}\end{array}$$

代码

class Solution {
    public int uniquePaths(int m, int n) {
        int[][] dp = new int[m][n];
        int i, j;
        for (i = 0; i < m; ++i) {
            for (j = 0; j < n; ++j) {
                if (i == 0 || j == 0) {
                    dp[i][j] = 1;
                } else {
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        return dp[m - 1][n - 1];
    }
}

63.不同路径II

文章

代码随想录|0063.不同路径II

思路

$$\begin{array}{c}dp[i][j]=\{\begin{array}{rlr}0& ,& obstacleGrid[i][j]=0\\ 1& ,& obstacleGrid[i][j]\ne 0\wedge i=0\wedge j=0\\ dp[i][j-1]& ,& i=0\wedge j>0\\ dp[i-1][j]& ,& j=0\wedge i>0\\ dp[i-1][j]+dp[i][j-1]& ,& else\end{array}\end{array}$$

代码

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m, n;
        m = obstacleGrid.length;
        n = obstacleGrid[0].length;
        int i, j;
        int[][] dp = new int[m][n];
        for (i = 0; i < m; ++i) {
            for (j = 0; j < n; ++j) {
                if (obstacleGrid[i][j] == 1) {
                    dp[i][j] = 0;
                } else if (i == 0 && j != 0) {
                    dp[i][j] = dp[i][j - 1] == 0 ? 0 : 1;
                } else if (i != 0 && j == 0) {
                    dp[i][j] = dp[i - 1][j] == 0 ? 0 : 1;
                } else if (i == 0 && j == 0) {
                    dp[i][j] = 1;
                }else {
                    dp[i][j] = dp[i][j - 1] + dp[i - 1][j];
                }
            }
        }
        return dp[m - 1][n - 1];
    }
}

总结

N刷不多说了