【DP】62.不同路径

题目

Python

class Solution:
    def uniquePaths(self, m: int, n: int) -> int:
        dp = [[0]*n for _ in range(m)]
        for i in range(m):
            dp[i][0] = 1
        for j in range(n):
            dp[0][j] = 1

        for i in range(1, m):
            for j in range(1, n):
                dp[i][j] = dp[i-1][j] + dp[i][j-1]

        return dp[m-1][n-1]

Java

法1：二维DP

必须掌握！

class Solution {
    public int uniquePaths(int m, int n) {
        int[][] matrix = new int[m][n];
        Arrays.fill(matrix[0], 1);
        for (int i = 0; i < m; ++i) {
            matrix[i][0] = 1;
        }
        for (int i = 1; i < m; ++i) {
            for (int j = 1; j < n; ++j) {
                matrix[i][j] = matrix[i - 1][j] + matrix[i][j - 1];
            }
        }

        return matrix[m - 1][n - 1];
    }
}