solve: Week 03 combination sum

Author: eunice-hong

combination-sum/eunice-hong.ts

@@ -0,0 +1,41 @@
+/**
+ * Finds all unique combinations of numbers from the candidates array that sum up to the target.
+ * 
+ * @param candidates - An array of numbers.
+ * @param target - The target sum.
+ * @returns An array of arrays, each containing a unique combination of numbers that sum up to the target.
+ * 
+ * Time Complexity: O(n^2)
+ * Space Complexity: O(n)
+ */
+function combinationSum(candidates: number[], target: number): number[][] {
+    // 1. Initialize result array
+    let combinations: number[][] = [];
+    let candidate: number[] = [];
+
+    // 2. Define recursive function
+    function combination(start: number, total: number) {
+        console.log(`start:${start}, total:${total}`)
+        if (target < total) {
+          // 3. If total is greater than target, return
+            return;
+        } else if (target === total) {
+            // 4. If total is equal to target, push candidate to result
+            combinations.push([...candidate])
+            return;
+        } else {
+          // 5. If total is less than target, iterate through candidates
+            for (let i = start; i < candidates.length; i++) {
+                // 6. Push candidate to result
+                candidate.push(candidates[i])
+                // 7. Recursively call combination function
+                combination(i, total + candidates[i])
+                // 8. Pop candidate from result
+                candidate.pop();
+            }
+        }
+    }
+    combination(0, 0);
+
+    return combinations;
+};