Add unique-paths solution in TypeScript

Author: Jeehay28

unique-paths/Jeehay28.ts

@@ -0,0 +1,41 @@
+// Memoized DFS
+// TC: O(m * n)
+// SC: O(m * n)
+function uniquePaths(m: number, n: number): number {
+  const memo = new Map<string, number>();
+
+  const traverse = (row: number, col: number) => {
+    if (row >= m || col >= n) return 0;
+    if (row === m - 1 && col === n - 1) return 1;
+    const key = `${row}-${col}`;
+    if (memo.has(key)) return memo.get(key);
+
+    const result = traverse(row + 1, col) + traverse(row, col + 1);
+    memo.set(key, result);
+    return result;
+  };
+
+  return traverse(0, 0);
+}
+
+// DP
+// TC: O(m * n)
+// SC: O(m * n)
+/*
+function uniquePaths(m: number, n: number): number {
+
+    // 1,     1,      1
+    // 1,  1+1=2, 1+(1+1)=3
+
+    const dp = Array.from({length: m}, () => Array(n).fill(1));
+
+    for(let i=1; i<m; i++) {
+        for(let j=1; j<n; j++) {
+            dp[i][j] = dp[i-1][j] + dp[i][j-1]
+        }
+    }
+
+    return dp[m-1][n-1];
+};
+*/
+