LeetCode 0851. Loud and Rich Solution in Java, C++, Python & More | Explanation + Code

Description

There is a group of n people labeled from 0 to n - 1 where each person has a different amount of money and a different level of quietness.

You are given an array richer where richer[i] = [ai, bi] indicates that ai has more money than bi and an integer array quiet where quiet[i] is the quietness of the ith person. All the given data in richer are logically correct (i.e., the data will not lead you to a situation where x is richer than y and y is richer than x at the same time).

Return an integer array answer where answer[x] = y if y is the least quiet person (that is, the person y with the smallest value of quiet[y]) among all people who definitely have equal to or more money than the person x.

 

Example 1:

Input: richer = [[1,0],[2,1],[3,1],[3,7],[4,3],[5,3],[6,3]], quiet = [3,2,5,4,6,1,7,0]
Output: [5,5,2,5,4,5,6,7]
Explanation: 
answer[0] = 5.
Person 5 has more money than 3, which has more money than 1, which has more money than 0.
The only person who is quieter (has lower quiet[x]) is person 7, but it is not clear if they have more money than person 0.
answer[7] = 7.
Among all people that definitely have equal to or more money than person 7 (which could be persons 3, 4, 5, 6, or 7), the person who is the quietest (has lower quiet[x]) is person 7.
The other answers can be filled out with similar reasoning.

Example 2:

Input: richer = [], quiet = [0]
Output: [0]

 

Constraints:

• n == quiet.length
• 1 <= n <= 500
• 0 <= quiet[i] < n
• All the values of quiet are unique.
• 0 <= richer.length <= n * (n - 1) / 2
• 0 <= ai, bi < n
• ai != bi
• All the pairs of richer are unique.
• The observations in richer are all logically consistent.

Solutions

Solution 1

PythonJavaC++GoTypeScript

class Solution: def loudAndRich(self, richer: List[List[int]], quiet: List[int]) -> List[int]: def dfs(i: int): if ans[i] != -1: return ans[i] = i for j in g[i]: dfs(j) if quiet[ans[j]] < quiet[ans[i]]: ans[i] = ans[j] g = defaultdict(list) for a, b in richer: g[b].append(a) n = len(quiet) ans = [-1] * n for i in range(n): dfs(i) return ans(code-box)

class Solution { private List<Integer>[] g; private int n; private int[] quiet; private int[] ans; public int[] loudAndRich(int[][] richer, int[] quiet) { n = quiet.length; this.quiet = quiet; g = new List[n]; ans = new int[n]; Arrays.fill(ans, -1); Arrays.setAll(g, k -> new ArrayList<>()); for (var r : richer) { g[r[1]].add(r[0]); } for (int i = 0; i < n; ++i) { dfs(i); } return ans; } private void dfs(int i) { if (ans[i] != -1) { return; } ans[i] = i; for (int j : g[i]) { dfs(j); if (quiet[ans[j]] < quiet[ans[i]]) { ans[i] = ans[j]; } } } }(code-box)

class Solution { public: vector<int> loudAndRich(vector<vector<int>>& richer, vector<int>& quiet) { int n = quiet.size(); vector<vector<int>> g(n); for (auto& r : richer) { g[r[1]].push_back(r[0]); } vector<int> ans(n, -1); function<void(int)> dfs = [&](int i) { if (ans[i] != -1) { return; } ans[i] = i; for (int j : g[i]) { dfs(j); if (quiet[ans[j]] < quiet[ans[i]]) { ans[i] = ans[j]; } } }; for (int i = 0; i < n; ++i) { dfs(i); } return ans; } };(code-box)

func loudAndRich(richer [][]int, quiet []int) []int { n := len(quiet) g := make([][]int, n) ans := make([]int, n) for i := range g { ans[i] = -1 } for _, r := range richer { a, b := r[0], r[1] g[b] = append(g[b], a) } var dfs func(int) dfs = func(i int) { if ans[i] != -1 { return } ans[i] = i for _, j := range g[i] { dfs(j) if quiet[ans[j]] < quiet[ans[i]] { ans[i] = ans[j] } } } for i := range ans { dfs(i) } return ans }(code-box)

function loudAndRich(richer: number[][], quiet: number[]): number[] { const n = quiet.length; const g: number[][] = new Array(n).fill(0).map(() => []); for (const [a, b] of richer) { g[b].push(a); } const ans: number[] = new Array(n).fill(-1); const dfs = (i: number) => { if (ans[i] != -1) { return ans; } ans[i] = i; for (const j of g[i]) { dfs(j); if (quiet[ans[j]] < quiet[ans[i]]) { ans[i] = ans[j]; } } }; for (let i = 0; i < n; ++i) { dfs(i); } return ans; }(code-box)