View Compilation Error

0_0_6678752_25452.cpp: In function `double dist(point, point)':
0_0_6678752_25452.cpp:20: error: `sqrt' undeclared (first use this function)
0_0_6678752_25452.cpp:20: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6678752_25452.cpp: In function `int main()':
0_0_6678752_25452.cpp:64: error: `qsort' undeclared (first use this function)