feat: solve No.997

901-1000/997. Find the Town Judge.md

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+# 997. Find the Town Judge
+
+- Difficulty: Easy.
+- Related Topics: Array, Hash Table, Graph.
+- Similar Questions: Find the Celebrity.
+
+## Problem
+
+In a town, there are `n` people labeled from `1` to `n`. There is a rumor that one of these people is secretly the town judge.
+
+If the town judge exists, then:
+
+
+
+- The town judge trusts nobody.
+
+- Everybody (except for the town judge) trusts the town judge.
+
+- There is exactly one person that satisfies properties **1** and **2**.
+
+
+You are given an array `trust` where `trust[i] = [ai, bi]` representing that the person labeled `ai` trusts the person labeled `bi`. If a trust relationship does not exist in `trust` array, then such a trust relationship does not exist.
+
+Return **the label of the town judge if the town judge exists and can be identified, or return **`-1`** otherwise**.
+
+
+Example 1:
+
+```
+Input: n = 2, trust = [[1,2]]
+Output: 2
+```
+
+Example 2:
+
+```
+Input: n = 3, trust = [[1,3],[2,3]]
+Output: 3
+```
+
+Example 3:
+
+```
+Input: n = 3, trust = [[1,3],[2,3],[3,1]]
+Output: -1
+```
+
+
+**Constraints:**
+
+
+
+- `1 <= n <= 1000`
+
+- `0 <= trust.length <= 104`
+
+- `trust[i].length == 2`
+
+- All the pairs of `trust` are **unique**.
+
+- `ai != bi`
+
+- `1 <= ai, bi <= n`
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number} n
+ * @param {number[][]} trust
+ * @return {number}
+ */
+var findJudge = function(n, trust) {
+    var map = Array(n + 1).fill(0).map(() => [0, 0]);
+    for (var i = 0; i < trust.length; i++) {
+        map[trust[i][0]][0] += 1;
+        map[trust[i][1]][1] += 1;
+    }
+    for (var j = 1; j <= n; j++) {
+        if (map[j][0] === 0 && map[j][1] === n - 1) return j;
+    }
+    return -1;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).