feat: unique-paths

Author: minji-go

unique-paths/minji-go.java

@@ -0,0 +1,39 @@
+/**
+ * <a href="https://leetcode.com/problems/unique-paths/">week07-4. unique-paths</a>
+ * <li>Description: return the number of possible unique paths to reach the bottom-right corner</li>
+ * <li>Topics: Math, Dynamic Programming, Combinatorics </li>
+ * <li>Time Complexity: O(M×N), Runtime 2ms             </li>
+ * <li>Space Complexity: O(M×N), Memory 40.76MB         </li>
+ */
+class Solution {
+    public int uniquePaths(int m, int n) {
+        int[][] dirs = {{1, 0}, {0, 1}};
+        int[][] dp = new int[m][n];
+        dp[0][0] = 1;
+
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{0, 0});
+
+        while (!queue.isEmpty()) {
+            int[] cur = queue.poll();
+            int cr = cur[0];
+            int cc = cur[1];
+
+            for (int i = 0; i < 2; i++) {
+                int nr = cr + dirs[i][0];
+                int nc = cc + dirs[i][1];
+
+                if (nr > m - 1 || nc > n - 1) {
+                    continue;
+                }
+
+                if (dp[nr][nc] == 0) {
+                    queue.add(new int[]{nr, nc});
+                }
+                dp[nr][nc] += dp[cr][cc];
+            }
+        }
+
+        return dp[m - 1][n - 1];
+    }
+}