Read integer
while(~scanf("%d",&x)){/* do something */}Since scanf() returns EOF when end-of-file is reached while reading,
this while-loop read one integer to x until it reaches end-of-file.
EOF usally defined as -1, and ~(-1) == 0.
So when scanf() reads EOF, which indicates end-of-file, that while-loop terminates.
Discard first line
gets(x); /* x must be pointer */Loop [n-1, 0]
while(n--){/* do something */}
for(;n--;){/* do something */}