Given a non-negative number **n**. The problem is to toggle the last **m** bits in the binary representation of **n**. A **toggle** operation flips a bit **0** to **1** and a bit **1** to **0**.

**Constraint:** 1 <= m <= n.

Examples:

Input : n = 21, m = 2 Output : 22(21)= (101_{10}01)_{2}(22)= (101_{10}10)_{2}The last two bits in the binary representation of21are toggled. Input : n = 107, m = 4 Output : 100

**Approach:** Following are the steps:

- Calculate
**num**= (1 << m) – 1. This will produce a number**num**having**m**number of bits and all will be set. - Now, perform
**n = n ^ num**. This will toggle the last**m**bits in**n**.

// C++ implementation to toggle the last m bits #include <bits/stdc++.h> using namespace std; // function to toggle the last m bits unsigned int toggleLastMBits(unsigned int n, unsigned int m) { // calculating a number 'num' having 'm' bits // and all are set unsigned int num = (1 << m) - 1; // toggle the last m bits and return the number return (n ^ num); } // Driver program to test above int main() { unsigned int n = 107; unsigned int m = 4; cout << toggleLastMBits(n, m); return 0; }

Output:

100

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