SGU 106 The equation
分情况讨论
扩展欧几里得
代码是按别人的思路改的。。
1 /*Author :usedrose */ 2 /*Created Time :2015/7/25 14:51:42*/ 3 /*File Name :2.cpp*/ 4 #include <cstdio> 5 #include <iostream> 6 #include <algorithm> 7 #include <sstream> 8 #include <cstdlib> 9 #include <cstring> 10 #include <climits> 11 #include <vector> 12 #include <string> 13 #include <ctime> 14 #include <cmath> 15 #include <deque> 16 #include <queue> 17 #include <stack> 18 #include <set> 19 #include <map> 20 #define INF 0x3f3f3f3f 21 #define eps 1e-8 22 #define pi acos(-1.0) 23 #define MAXN 1110 24 #define OK cout << "ok" << endl; 25 #define o(a) cout << #a << " = " << a << endl 26 #define o1(a,b) cout << #a << " = " << a << " " << #b << " = " << b << endl 27 using namespace std; 28 typedef long long LL; 29 30 void exgcd(LL a, LL b, LL &d, LL &x, LL &y) 31 { 32 if (!b) d = a, x = 1, y = 0; 33 else { 34 exgcd(b, a%b, d, y, x); 35 y -= x*(a/b); 36 } 37 } 38 39 int main() 40 { 41 //freopen("data.in","r",stdin); 42 //freopen("data.out","w",stdout); 43 cin.tie(0); 44 ios::sync_with_stdio(false); 45 LL a, b, c, d, x, y, x1, x2, y1, y2; 46 while (cin >> a >> b >> c) { 47 cin >> x1 >> x2 >> y1 >> y2; 48 if (a == 0 || b == 0) { 49 if (a == 0 && b) { 50 if (c%b || c/b > y2 || c/b < y1) cout << "0" << endl; 51 else cout << x2 - x1 + 1 << endl; 52 } 53 else if (b == 0 && a) { 54 if (c%a || c/a > x1 || c/b < x1) cout << "0" << endl; 55 else cout << y2 - y1 + 1 << endl; 56 } 57 else { 58 if (c) cout << "0" << endl; 59 else cout << (x2 - x1 + 1)*(y2 - y1 + 1) << endl; 60 } 61 } 62 else { 63 if (c < 0) c = -c; 64 else a = -a, b = -b; 65 if (a < 0) { 66 a = -a; 67 x1 = -x1; 68 x2 = -x2; 69 swap(x1, x2); 70 } 71 if (b < 0) { 72 b = -b; 73 y1 = -y1; 74 y2 = -y2; 75 swap(y1, y2); 76 } 77 if (a < b) exgcd(b, a, d, y, x); 78 else exgcd(a, b, d, x, y); 79 if (c%d) { 80 cout << "0" << endl; 81 continue; 82 } 83 a /= d, b /= d, c /= d; 84 //小优化 85 while(x < x1) x += b, y -= a; 86 while(x > x2) x -= b, y += a; 87 LL ans = 0; 88 bool in = false; 89 x *= c, y *= c; 90 while (x <= x2) { 91 if (x >= x1 && x <= x2 && y >= y1 && y <= y2) { 92 in = true; 93 break; 94 } 95 x += b, y -= a; 96 } 97 while (!in && x >= x1) { 98 if (x >= x1 && x <= x2 && y >= y1 && y <= y2) { 99 in = true; 100 break; 101 } 102 x -= b, y += a; 103 } 104 if (in) { 105 ans += min((x2-x)/b, (y-y1)/a); 106 ans += min((x-x1)/b, (y2-y)/a); 107 } 108 cout << ans + in << endl; 109 } 110 } 111 return 0; 112 }
