【正经题解】最少问题

#include<bits/stdc++.h>
using namespace std;

int start_num, target_num, visited[100005];

struct Node {
    int value, steps;
};

// 广度优先搜索
void bfs() {
    queue<Node> q;
    q.push({start_num, 0});
    visited[start_num] = 1;

    while (!q.empty()) {
        Node cur = q.front();
        q.pop();

        // 判断是否达到目标值
        if (cur.value == target_num) {
            cout << cur.steps;
            return;
        }

        // 尝试减1
        if (cur.value - 1 >= 0 && !visited[cur.value - 1]) {
            visited[cur.value - 1] = 1;
            q.push({cur.value - 1, cur.steps + 1});
        }

        // 尝试加1
        if (cur.value + 1 <= 100000 && !visited[cur.value + 1]) {
            visited[cur.value + 1] = 1;
            q.push({cur.value + 1, cur.steps + 1});
        }

        // 尝试乘2
        if (cur.value * 2 <= 100000 && !visited[cur.value * 2]) {
            visited[cur.value * 2] = 1;
            q.push({cur.value * 2, cur.steps + 1});
        }
    }
}

int main() {
    cin >> start_num >> target_num;
    bfs();
    return 0;
}