LintCode "Update Bits"

class Solution {
public:
    /**
     *@param n, m: Two integer
     *@param i, j: Two bit positions
     *return: An integer
     */
    int updateBits(int n, int m, int i, int j) {
        if (i == 0 && j == 31) return m;
        
        int cnt = j - i + 1;
        int mask = (1 << cnt) - 1;
        int nn = (n >> i) & mask;
        n ^= (nn << i); // clear
        n |= (m << i); // set
        
        return n;
    }
};