C41/T4 最难题题解-全网首发

#include <iostream>
#include <queue>
#include <vector>
#include <utility>
using namespace std;
int bfs(int a, int b) {
    vector<bool> visited(10005, false);
    queue<pair<int, int>> q;
    q.push({a, 0});
    visited[a] = true;
    while (!q.empty()) {
        auto [current, steps] = q.front();
        q.pop();
        if (current == b) {
            return steps;
        }
        int next1 = current * 2;
        if (next1 <= 10000 && !visited[next1]) {
            q.push({next1, steps + 1});
            visited[next1] = true;
        }
        int next2 = current - 1;
        if (next2 >= 0 && !visited[next2]) {
            q.push({next2, steps + 1});
            visited[next2] = true;
        }
    }
    return -1;
}
int main() {
    int T;
    cin >> T;
    while (T--) {
        int a, b;
        cin >> a >> b;
        cout << bfs(a, b) << endl;
    }
    return 0;
}