feat(LeetCode): ✨ add diffWaysToCompute (lc. 0241)

Author: rain84

src/leetcode/dsa/dynamic-programming/0241-diffWaysToCompute.test.ts

@@ -0,0 +1,19 @@
+import { diffWaysToCompute } from './0241-diffWaysToCompute'
+
+it.each(
+  //  prettier-ignore
+  [
+    [
+      "2-1-1",
+      [0,2]
+    ],
+    [
+      "2*3-4*5",
+      [-34,-14,-10,-10,10]
+    ]
+  ]
+)('should work %#', (input, output) => {
+  expect(sort(diffWaysToCompute(input))).toMatchObject(sort(output))
+})
+
+const sort = (nums: number[]) => nums.sort((a, b) => a - b)

src/leetcode/dsa/dynamic-programming/0241-diffWaysToCompute.ts

@@ -0,0 +1,38 @@
+/**
+ * {@link https://leetcode.com/problems/different-ways-to-add-parentheses/ | 241. Different Ways to Add Parentheses}
+ *
+ * Topics: Math | String | Dynamic Programming | Recursion | Memoization
+ */
+export function diffWaysToCompute(expression: string): number[] {
+  const cache = new Map<string, number[]>()
+  const operators = new Set(['+', '-', '*'])
+
+  const dfs = (exp: string): number[] => {
+    if (!exp) return []
+    if (cache.has(exp)) return cache.get(exp)!
+    if (Number.isInteger(+exp)) return [+exp]
+
+    const res: number[] = []
+    const n = exp.length
+
+    for (let i = 0; i < n; i++) {
+      const ch = exp[i]
+      if (!operators.has(ch)) continue
+
+      const [left, right] = [dfs(exp.slice(0, i)), dfs(exp.slice(i + 1))]
+      for (const x of left) {
+        for (const y of right) {
+          if (ch === '+') res.push(x + y)
+          if (ch === '-') res.push(x - y)
+          if (ch === '*') res.push(x * y)
+        }
+      }
+    }
+
+    cache.set(exp, res)
+
+    return res
+  }
+
+  return dfs(expression)
+}