//二进制中1的个数
//把整数转化为字符串
//把字符串转化为整数
//二进制中1的个数
int hammingWeight(int n) {
int ans = 0;
while (n)
{
n ^= (n&(-n));
ans++;
}
return ans;
}
//把整数转化为字符串
char* itoa(int num,char* str,int radix) //copy from 百度百科
{/*索引表*/
char index[]="0123456789ABCDEF";
unsigned unum;/*中间变量*/
int i=0,j,k;
/*确定unum的值*/
if(radix==10&&num<0)/*十进制负数*/
{
unum=(unsigned)-num;
str[i++]='-';
}
else unum=(unsigned)num;/*其他情况*/
/*转换*/
do{
str[i++]=index[unum%(unsigned)radix];
unum/=radix;
}while(unum);
str[i]='\0';
/*逆序*/
if(str[0]=='-') k=1;/*十进制负数*/
else k=0;
for(j=k;j<=(i-1)/2;j++)
{
char temp;
temp=str[j];
str[j]=str[i-1+k-j];
str[i-1+k-j]=temp;
}
return str;
}
//把字符串转化为整数
int atoi(const char *nptr,int radix) //copy from somebody
{
while ( isspace((int)(unsigned char)*nptr) ) ++nptr;/* skip whitespace */
int c = (int)(unsigned char)*nptr++;
int sign = c; /* save sign indication */
if (c == '-' || c == '+') c = (int)(unsigned char)*nptr++; /* skip sign */
int total = 0;
while (isdigit(c)) {
total = radix * total + (c - '0'); /* accumulate digit */
c = (int)(unsigned char)*nptr++; /* get next char */
}
if (sign == '-') return -total;
else return total; /* return result, negated if necessary */
}