day34：动态规划part2

62.不同路径

class Solution {public int uniquePaths(int m, int n) {// dp[i][j]：到达(i, j)的路径数量int[][] dp = new int[m][n];for (int j = 0; j < n; j++) dp[0][j] = 1;for (int i = 1; i < m; i++) dp[i][0] = 1;for (int i = 1; i < m; i++)for (int j = 1; j < n; j++)dp[i][j] = dp[i - 1][j] + dp[i][j - 1];return dp[m - 1][n - 1];}
}

63.不同路径 II

class Solution {public int uniquePathsWithObstacles(int[][] obstacleGrid) {int m = obstacleGrid.length;int n = obstacleGrid[0].length;int[][] dp = new int[m][n];for (int j = 0; j < n && obstacleGrid[0][j] == 0; j++) dp[0][j] = 1;// 都从0开始，防止起点有障碍物的情况for (int i = 0; i < m && obstacleGrid[i][0] == 0; i++) dp[i][0] = 1;for (int i = 1; i < m; i++)for (int j = 1; j < n; j++)if (obstacleGrid[i][j] == 0)dp[i][j] = dp[i - 1][j] + dp[i][j - 1];return dp[m - 1][n - 1];}
}