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*[codility]Country network

https://codility.com/programmers/challenges/fluorum2014

http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1273

http://blog.csdn.net/caopengcs/article/details/36872627

http://www.quora.com/How-do-I-determine-the-order-of-visiting-all-leaves-of-a-rooted-tree-so-that-in-each-step-I-visit-a-leaf-whose-path-from-root-contains-the-most-unvisited-nodes#

思路如曹博所说,先dfs记录离根的距离,来的方向的前驱。然后按距离排序,之后按此排序求有意义的增加距离。

直观感受是,如果两个叶子在一个分叉上,显然深的节点更先被访问,如果不在一个分叉上,那么先算深的也没什么损失。最后,按照这个权值再对叶子排序一次,就是所要的结果。

#include <iostream>using namespace std;void dfs(vector<vector<int>> &tree, vector<int> &parent, vector<int> &depth, vector<bool> &visited, int root, int dep) {    visited[root] = true;    depth[root] = dep;    for (int i = 0; i < tree[root].size(); i++) {        if (visited[tree[root][i]])            continue;        parent[tree[root][i]] = root;        dfs(tree, parent, depth, visited, tree[root][i], dep + 1);    }}vector<int> solution(int K, vector<int> &T) {    int n = T.size();    vector<vector<int>> tree(n);    for (int i = 0; i < n; i++) {        if (T[i] != i) {            tree[i].push_back(T[i]);            tree[T[i]].push_back(i);        }    }    vector<int> parent(n);    vector<int> depth(n);    vector<bool> visited(n);    dfs(tree, parent, depth, visited, K, 0);    vector<vector<int>> cnt(n);    for (int i = 0; i < n; i++) {        cnt[depth[i]].push_back(i);        }    vector<int> ordered;    for (int i = n - 1; i >= 0; i--) {        for (int j = 0; j < cnt[i].size(); j++) {            ordered.push_back(cnt[i][j]);            }    }    vector<int> res;    vector<int> length(n);    visited.clear();    visited.resize(n);    visited[K] = true;    for (int i = 0; i < ordered.size(); i++) {        int len = 0;        int x = ordered[i];        while (!visited[x]) {            visited[x] = true;            x = parent[x];            len++;        }        length[ordered[i]] = len;        //cout << "length[" << ordered[i] << "]:" << len << endl;    }        cnt.clear();    cnt.resize(n);    for (int i = 0; i < length.size(); i++) {        cnt[length[i]].push_back(i);        }    res.push_back(K);    for (int i = cnt.size() - 1; i > 0; i--) {        for (int j = 0; j < cnt[i].size(); j++) {            res.push_back(cnt[i][j]);        }    }    return res;}

  

*[codility]Country network