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Maximize a given unsigned number by swapping bits at its extreme positions in C++
Problem statement
Given a number maximize it by swapping bits at its extreme positions i.e. at first and last position, second and second last position and so on.
If the input number is 8 then its binary representation is−
00000000 00000000 00000000 00001000
After swapping bits at extreme positions number becomes −
00010000 00000000 00000000 00000000 and its decimal equivalent is: 268435456
Algorithm
1. Create a copy of the original number 2. If less significant bit is 1 and more significant bit is 0 then swap the bits in the bit from only, continue the process until less significant bit’s position is less than more significant bit’s position 3. Return new number
Example
#include <bits/stdc++.h>
#define ull unsigned long long
using namespace std;
ull getMaxNumber(ull num){
ull origNum = num;
int bitCnt = sizeof(ull) * 8 - 1;
int cnt = 0;
for(cnt = 0; cnt < bitCnt; ++cnt, --bitCnt) {
int m = (origNum >> cnt) & 1;
int n = (origNum >> bitCnt) & 1;
if (m > n) {
int x = (1 << cnt | 1 << bitCnt);
num = num ^ x;
}
}
return num;
}
int main(){
ull num = 8;
cout << "Maximum number = " << getMaxNumber(num) << endl;
return 0;
}Output
When you compile and execute the above program. It generates the following output −
Maximum number = 268435456
Updated on: 24-Dec-2019
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