feat: leetcode 710

Author: deweyou

problemset/random-pick-with-blacklist/README.md

@@ -35,4 +35,43 @@ solution.pick(); // 返回 6
 solution.pick(); // 返回 1
 solution.pick(); // 返回 0
 solution.pick(); // 返回 4
+```
+
+## 解题
+
+```ts
+/**
+ * 黑名单映射
+ */
+export class Solution {
+  bound: number
+  b2w: Map<number, number>
+
+  constructor(n: number, blacklist: number[]) {
+    this.b2w = new Map<number, number>()
+    const len = blacklist.length
+    this.bound = n - len
+    const black = new Set()
+
+    for (const b of blacklist) {
+      if (b >= this.bound)
+        black.add(b)
+    }
+
+    let w = this.bound
+    for (const b of blacklist) {
+      if (b < this.bound) {
+        while (black.has(w)) w++
+
+        this.b2w.set(b, w)
+        w++
+      }
+    }
+  }
+
+  pick(): number {
+    const x = Math.floor(Math.random() * this.bound)
+    return this.b2w.get(x) || x
+  }
+}
 ```

problemset/random-pick-with-blacklist/index.ts

@@ -1,3 +1,6 @@
+/**
+ * 黑名单映射
+ */
 export class Solution {
   bound: number
   b2w: Map<number, number>