HDU - 3038 How Many Answers Are Wrong (带权并查集)
2014-07-02 11:02
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题意:n个数,m次询问,每次问区间a到b之间的和为s,问有几次冲突
思路:带权并查集的应用,[a, b]和为s,所以a-1与b就可以确定一次关系,通过计算与根的距离可以判断出询问的正确性
思路:带权并查集的应用,[a, b]和为s,所以a-1与b就可以确定一次关系,通过计算与根的距离可以判断出询问的正确性
#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> using namespace std; const int MAXN = 200010; int f[MAXN],arr[MAXN]; int m,n; int find(int x) { if (f[x] == x) return x; int tmp = find(f[x]); arr[x] += arr[f[x]]; return f[x] = tmp; } int main() { while (scanf("%d%d", &n, &m) != EOF) { for (int i = 0; i <= n; i++) f[i] = i; memset(arr, 0, sizeof(arr)); int ans = 0; for (int t = 0; t < m; t++) { int a,b,s; scanf("%d%d%d", &a, &b, &s); a--; int f1 = find(a); int f2 = find(b); if (f1 != f2) { f[f2] = f1; arr[f2] = arr[a]+s-arr[b]; } else if (arr[b]-arr[a] != s) ans++; } printf("%d\n", ans); } return 0; }
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