《Cracking the Coding Interview》——第7章：数学和概率论——题目3

 1 // 7.3 Given two lines on the Cartesian, determine if they would intersect.
 2 #include <cstdio>
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     // a * x + b * y + c = 0;
 8     // d * x + e * y + f = 0;
 9     int a, b, c, d, e, f;
10     bool suc;
11     
12     while (scanf("%d%d%d%d%d%d", &a, &b, &c, &d, &e, &f) == 6) {
13         if ((a == 0 && b == 0) || (d == 0 && e == 0)) {
14             // invalid line
15             suc = false;
16         } else if (a * e == b * d) {
17             if (a * f == c *d) {
18                 // coincident
19                 suc = true;
20             } else {
21                 // parallel
22                 suc = false;
23             }
24         } else {
25             // intersect
26             suc = true;
27         }
28         if (suc) {
29             printf("Yes\n");
30         } else {
31             printf("No\n");
32         }
33     }
34     
35     return 0;
36 }