43 lines
949 B
C++
43 lines
949 B
C++
#include <bits/stdc++.h>
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using namespace std;
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const int N = 100010;
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typedef pair<int,int> PII;
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int n;
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int a, b;
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int k[N];
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int st[N];
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queue<PII> q;
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int step = -1;
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void bfs() {
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//初始化队列
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q.push({a, 0});
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st[a] = 1;
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while (q.size()) {
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auto t = q.front();
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q.pop();
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if (t.first == b) {
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step = t.second;
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break;
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}
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int x = t.first + k[t.first];
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if (x <= n && !st[x]) {
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q.push({x, t.second + 1});
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st[x] = 1;
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}
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x = t.first - k[t.first];
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if (x >= 1 && !st[x]) {
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q.push({x, t.second + 1});
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st[x] = 1;
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}
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}
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}
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int main() {
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//n是几层楼，a:从几层出发 ,b:到几层去
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cin >> n >> a >> b;
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for (int i = 1; i <= n; i++) cin >> k[i]; //记录每层楼的可以按下的数字
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bfs();
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printf("%d", step);
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return 0;
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} |