Center of gravity of POJ-1655 balancing act tree

B. exactly match the center of gravity of the tree: Find a vertex, and the largest subtree node in all its Subtrees is the least.

The Code is as follows:

# Include <cstdlib> # include <cstring> # include <cstdio> # include <iostream> # include <algorithm> # define maxn 20000 using namespace STD; // to put it bluntly, this question is to find the center of gravity int N and idx of a tree; // It indicates that there are n nodes. // due to the large number of nodes, the number of nodes is sparse, therefore, the struct node {int X, next, CNT; // CNT is stored in the form of an adjacent table to indicate that the node connected to this edge is the total number of nodes in the subtree bool vis ;} E [(maxn <1) + 5]; // int head [maxn + 5] caused by bidirectional edges; void addedge (int A, int B) {++ idx; E [idx]. vis = false, E [idx]. CNT = 0; E [idx]. X = B, E [idx ]. Next = head [a]; head [a] = idx;} int DFS (int x) {// obtain the number of nodes in the subtree connected by an edge (the entrance edge is not calculated; otherwise, all nodes are N) int sum = 0; for (INT I = head [X]; I! =-1; I = E [I]. Next) {If (! E [I]. vis) {// if this edge has not been accessed E [I]. vis = E [I ^ 1]. vis = true; E [I]. CNT + = DFS (E [I]. x); e [I ^ 1]. CNT = n-e [I]. CNT;} sum + = E [I]. CNT;} return sum + 1;} void solve (Int & X, Int & Y) {Y = 0x7fffffff; For (INT I = 1; I <= N; ++ I) {int max = 0x7fffffff + 1; for (int K = head [I]; k! =-1; k = E [K]. next) {max = max (max, E [K]. CNT) ;}if (max <Y) {Y = max; X = I ;}} int main () {int t; scanf ("% d ", & T); While (t --) {int A, B, X, Y; memset (Head, 0xff, sizeof (head); idx =-1; scanf ("% d", & N); For (INT I = 1; I <n; ++ I) {scanf ("% d", &, & B); addedge (a, B); addedge (B, A);} DFS (1); solve (x, y ); printf ("% d \ n", x, y);} return 0 ;}