Merge pull request SnowScriptWinterOfCode#528 from aishwarya-chandra/…

…day21q3

day21q3

Day-21/q3: Unique Paths/aishwarya--J.md

@@ -0,0 +1,17 @@
+```
+class Solution {
+  private int traverse(int i, int j, int[][] memo, int m, int n) {
+    if (i < 0 || j < 0 || i >= m || j >= n) return 0;
+    if (i == m-1 && j == n-1) return 1;
+    if (memo[i][j] != 0) return memo[i][j];
+    
+    memo[i][j] = traverse(i+1, j, memo, m, n) + traverse(i, j+1, memo, m, n);
+    return memo[i][j];
+  }
+  
+  public int uniquePaths(int m, int n) {
+    var memo = new int[m][n];
+    return traverse(0, 0, memo, m, n);
+  }
+}
+```