Remove methods from project

Depth-First Search Breadth-First Search Graph Theory

50.4% acceptance

Feb 23, 2026

156

You are maintaining a project that has n methods numbered from 0 to n - 1. You are given two integers n and k, and a 2D integer array invocations, where invocations[i] = [ai, bi] indicates that method ai invokes method bi. There is a known bug in method k. Method k, along with any method invoked by it, either directly or indirectly, are considered suspicious and we aim to remove them. A group of methods can only be removed if no method outside the group invokes any methods within it. Return an array containing all the remaining methods after removing all the suspicious methods. You may return the answer in any order. If it is not possible to remove all the suspicious methods, none should be removed.

Solution

Rust

Time O(n * m)

Space O(n * m)

LeetCode

solution.rs

impl Solution {
  pub fn remaining_methods(n: i32, k: i32, invocations: Vec<Vec<i32>>) -> Vec<i32> {
    let n = n as usize;
    let k = k as usize;
    let mut adj = vec![vec![]; n];
    for inv in &invocations {
      adj[inv[0] as usize].push(inv[1] as usize);
    }
    // BFS/DFS from k to find all suspicious methods
    let mut suspicious = vec![false; n];
    let mut stack = vec![k];
    suspicious[k] = true;
    while let Some(node) = stack.pop() {
      for &next in &adj[node] {
        if !suspicious[next] {
          suspicious[next] = true;
          stack.push(next);
        }
      }
    }
    // Check if any non-suspicious method invokes a suspicious method
    for inv in &invocations {
      let a = inv[0] as usize;
      let b = inv[1] as usize;
      if !suspicious[a] && suspicious[b] {
        // Cannot remove - return all
        return (0..n as i32).collect();
      }
    }
    // Return non-suspicious methods
    (0..n).filter(|&i| !suspicious[i]).map(|i| i as i32).collect()
  }
}