[leetcode] Unique Paths

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public class Solution { public int uniquePaths(int m, int n) { if (m <= 0 || n <= 0) return 0; int rollingWays[] = new int[n]; for (int i = 0; i < n; i++){ rollingWays[i] = 1; } for (int i = m-2; i >= 0; i--){ for (int j = n-2; j >= 0; j--){ rollingWays[j] = rollingWays[j]+rollingWays[j+1]; } } return rollingWays[0]; } }