int rangeBitwiseAnd(int m, int n) {
if (m == 0) {
return 0;
}
if (m == n) {
return m;
}
const integer_info mi = info(m), ni = info(n);
return ni.digits == mi.digits ? mi.fst + rangeBitwiseAnd(mi.rem, ni.rem) : 0;
}
//time complexity: O(1)
//space complexity: O(1)
//2A : missing the recursive part in line 24 caused the first failure
int rangeBitwiseAnd(int m, int n) {
if (m == 0) {
return 0;
}
if (m == n) {
return m;
}
int len1 = bitLength(m);
int len2 = bitLength(n);
if (len1 == len2) {
int leastNum = 1 << (len1 - 1);
return leastNum + rangeBitwiseAnd(m - leastNum, n - leastNum);
} else {
return 0;
}
}
int rangeBitwiseAnd(int m, int n) { return (n > m) ? (rangeBitwiseAnd(m/2, n/2) << 1) : m; }
int rangeBitwiseAnd(int m, int n) {
/// return 0xffffffff<<(int)floor(log(n-m))&n; //bug:n-m可能为0
return (0xffffffff << (int)ceil(log2(n-m+1))) & m & n;
或
return (n > m) ? (rangeBitwiseAnd(m/2, n/2) << 1) : m;
}
int main(){
int ret =rangeBitwiseAnd(5,7);
printf("ret:%d\n",ret);
puts("end of app");
}
