View Compilation Error

0_0_1668479_18422.cpp: In function `int main()':
0_0_1668479_18422.cpp:57: error: `scanf' undeclared (first use this function)
0_0_1668479_18422.cpp:57: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1668479_18422.cpp:61: error: `memset' undeclared (first use this function)
0_0_1668479_18422.cpp:70: error: `qsort' undeclared (first use this function)
0_0_1668479_18422.cpp:80: error: `printf' undeclared (first use this function)