cstdlib、cmath库用法总结

cstdlib

atof, atoi, atol, strtod, strtof, strtols, strtol, strtoll, strtoul, strtoull, rand, srand, calloc, free, malloc, realloc, abort, atexit, exit, getenv, system, bsearch, qsort, abs, div, labs, ldiv, llabs, tlldiv, mblen, mbtowc, wctomb, mbstowcs, wcstombs

• atof、atoi、atol

cout<<atoi("546.1")<<endl;//546
cout<<atof("546.1")<<endl;//546.1
cout<<atol("546.1")<<endl;//546

• strtod, strtof, strtols, strtol, strtoll, strtoul, strtoull

不仅可以字符串转数字，还可以顺带进制转换！

	string s;
	char *c;
	cout<<strtod("213.454mkomo",&c)<<endl;        //213.454
	cout<<c<<endl;                                //mkomo
	cout<<strtof("213.454mkomo",&c)<<endl;        //213.454
	cout<<c<<endl;                                //mkomo
	cout<<strtol("123456789.454mkomo",&c,3)<<endl;//5
	cout<<c<<endl;                                //3456789.454mkomo
	cout<<strtoll("213.454mkomo",&c,10)<<endl;    //213
	cout<<c<<endl;                                //.454mkomo
	cout<<strtoul("213.454mkomo",&c,10)<<endl;    //213
	cout<<c<<endl;                                //.454mkomo

• rand、srand

srand((unsigned)time(0));
cout<<rand()<<endl;

• abs、labs

cout<<abs(-45.67)<<endl;//45.67
cout<<labs(-45.67)<<endl;-45.67

cmath

• pow

cout<<pow(2,3)<<endl;//8

• sqrt
• fabs

cout<<fabs(-45.67)<<endl;//45.67