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
java复制代码
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];
}
}