48 lines
1.4 KiB
C++
48 lines
1.4 KiB
C++
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#include <bits/stdc++.h>
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using namespace std;
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const int N = 5005;
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pair<int, int> x[N]; //数据一对一对读入，用pair，或者创建一个struct
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int f[N];
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/*
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回想LIS问题中，线性序列的下标是递增的，我们求的也是其中最长的递增子序列，与本题如出一辙。所以解决本题
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只需要先对一边的坐标自小到大排序，排序后另一岸的友好城市成一个线性序列，求该序列的LIS长度即是本题的解。
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这个太牛了，真的在竞赛现场能想出办法吗？难道训练多了就会了？
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*/
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int main() {
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//输入+输出重定向
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freopen("../1280.txt", "r", stdin);
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int n;
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cin >> n;
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for (int i = 1; i <= n; i++) cin >> x[i].first >> x[i].second;
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//按pair的first进行排序，那么second自动配合上
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sort(x + 1, x + 1 + n);
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//输出看一下
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for (int i = 1; i <= n; ++i) {
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cout << x[i].first << "," << x[i].second << " ";
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}
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cout << endl;
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//转化为最长上升子序列问题
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for (int i = 1; i <= n; i++) {
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f[i] = 1;
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for (int j = 1; j < i; j++) {
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if (x[i].second > x[j].second) f[i] = max(f[i], f[j] + 1);
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}
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}
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int res = 0;
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//找出最大值
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for (int i = 1; i <= n; i++) res = max(res, f[i]);
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cout << res << endl;
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//关闭文件
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fclose(stdin);
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return 0;
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}
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