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Bit Manipulation

Find Most Significant Bit

Below implementation is using built-in function

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#include <bits/stdc++.h>
using namespace std;


int msb(int x) {
    return sizeof (int) * 8 - __builtin_clz(x);
}

int msb(long long x) {
    return sizeof(long long) * 8 - __builtin_clzll(x);
}


int main() {
    for (int x = 0; x < 10; ++x) {
        printf("x: %d, msb: %d\n", x, msb(x));
    }
    return 0;
}

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x: 0, msb: 0
x: 1, msb: 1
x: 2, msb: 2
x: 3, msb: 2
x: 4, msb: 3
x: 5, msb: 3
x: 6, msb: 3
x: 7, msb: 3
x: 8, msb: 4
x: 9, msb: 4

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