diff --git a/leetcode/0997.Find-the-Town-Judge/README.md b/leetcode/0997.Find-the-Town-Judge/README.md new file mode 100644 index 00000000..0b249ec4 --- /dev/null +++ b/leetcode/0997.Find-the-Town-Judge/README.md @@ -0,0 +1,87 @@ +# [997. Find the Town Judge](https://leetcode-cn.com/problems/find-the-town-judge/) + +## 题目 + +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. + +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 <= 10000 +- trust[i].length == 2 +- All the pairs of trust are unique. +- ai != bi +- 1 <= ai, bi <= n + +## 题目大意 + +小镇里有 n 个人,按从 1 到 n 的顺序编号。传言称,这些人中有一个暗地里是小镇法官。 + +如果小镇法官真的存在,那么: + +- 小镇法官不会信任任何人。 +- 每个人(除了小镇法官)都信任这位小镇法官。 +- 只有一个人同时满足属性 1 和属性 2 。 + +给你一个数组 trust ,其中 trust[i] = [ai, bi] 表示编号为 ai 的人信任编号为 bi 的人。 + +如果小镇法官存在并且可以确定他的身份,请返回该法官的编号;否则,返回 -1 。 + +## 解题思路 + +入度和出度统计 + +- 被人信任定义为入度, 信任别人定义为出度 +- 如果1-n之间有数字x的入度为n - 1,出度为0,则返回x + +## 代码 + +```go +package leetcode + +func findJudge(n int, trust [][]int) int { + if n == 1 && len(trust) == 0 { + return 1 + } + judges := make(map[int]int) + for _, v := range trust { + judges[v[1]] += 1 + } + for _, v := range trust { + if _, ok := judges[v[0]]; ok { + delete(judges, v[0]) + } + } + for k, v := range judges { + if v == n-1 { + return k + } + } + return -1 +} +``` \ No newline at end of file