07-Unique-Paths.md

Unique Paths

Problem Link

https://leetcode.com/problems/unique-paths/

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Pattern

• Grid DP

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Approach

Count ways to reach each cell from the top or left neighbor.

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Time Complexity

O(mn)

Space Complexity

O(n)

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Java Solution

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