Created
September 1, 2013 05:32
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http://acm.csu.edu.cn/OnlineJudge/problem.php?id=1317 The longest path on tree
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#include <cassert> | |
#include <cstdio> | |
#include <cstring> | |
#include <climits> | |
#include <vector> | |
#include <functional> | |
#include <algorithm> | |
const int N = 50000; | |
int edgeCount, firstEdge[N], to[N << 1], nextEdge[N << 1], length[N << 1]; | |
void addEdge(int u, int v, int w) { | |
to[edgeCount] = v; | |
length[edgeCount] = w; | |
nextEdge[edgeCount] = firstEdge[u]; | |
firstEdge[u] = edgeCount ++; | |
} | |
int answer; | |
int search(int p, int u) { | |
std::vector <int> paths(1, 0); | |
for (int iter = firstEdge[u]; iter != -1; iter = nextEdge[iter]) { | |
int v = to[iter]; | |
if (v != p) { | |
paths.push_back(search(u, v) + length[iter]); | |
} | |
} | |
std::sort(paths.begin(), paths.end(), std::greater <int>()); | |
if ((int)paths.size() >= 2) { | |
answer = std::max(answer, paths[0] + paths[1]); | |
} | |
return paths[0]; | |
} | |
int main() { | |
int n, m; | |
while (scanf("%d%d", &n, &m) == 2) { | |
assert(n - 1 == m); | |
edgeCount = 0; | |
memset(firstEdge, -1, sizeof(firstEdge)); | |
for (int i = 0; i < n - 1; ++ i) { | |
int a, b, c; | |
scanf("%d%d%d", &a, &b, &c); | |
a --, b --; | |
addEdge(a, b, c); | |
addEdge(b, a, c); | |
} | |
answer = INT_MIN; | |
search(-1, 0); | |
printf("%d\n", answer); | |
} | |
return 0; | |
} |
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