bzoj1407

先看一些推导：

#include<iostream>#include<cstdio>#include<algorithm>using namespace std;int n;int c[20], p[20], l[20];void exgcd(int a, int b, int &x, int &y, int &d){if (b == 0){d = a, x = 1, y = 0;return;}else{exgcd(b, a%b, y, x, d);y -= a / b*x;}}bool getans(int a, int b, int m,int x1,int x2){int x, y, gcd;exgcd(a, m, x, y, gcd);if (b%gcd != 0)return true;int mm = m / gcd;if (mm<0)mm = -mm;x = x*(b / gcd);x = ((x%mm) + mm) % mm;return x>min(x1, x2);}bool istrue(int m){for (int i = 0; i < n; i++){for (int j = i + 1; j < n; j++){if (!getans(p[i] - p[j], c[j] - c[i], m, l[i], l[j]))return false;}}return true;}int main(){scanf("%d", &n);int j=-1;for (int i = 0; i < n; i++){scanf("%d%d%d", &c[i], &p[i], &l[i]);j = max(j, c[i]);}for (;j<=1000000; j++)if (istrue(j))break;printf("%d\n", j);return 0;}