leetcode-bit

发表于 | 分类于 | 阅读次数:
字数统计: 410 | 阅读时长 ≈ 2

数1

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class Solution {
public:
    int hammingWeight(uint32_t n) {
        int res = 0;
        for (int i = 0; i < 32; ++i) {
            res += (n & 1);
            n = n >> 1;
        }
        return res;
    }
};

2的幂

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class Solution {
public:
    bool isPowerOfTwo(int n) {
        int cnt = 0;
        while (n > 0) {
            cnt += (n & 1);
            n >>= 1;
        }
        return cnt == 1;
    } 
};

class Solution {
public:
    bool isPowerOfTwo(int n) {
        return (n > 0) && (!(n & (n - 1)));
    } 
};

数字范围按位与

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class Solution {
public:
    int rangeBitwiseAnd(int m, int n) {
        int d = INT_MAX;
        while ((m & d) != (n & d)) {
            d <<= 1;
        }
        return m & d;
    }
};

重复的dna序列

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class Solution {
public:
    vector<string> findRepeatedDnaSequences(string s) {
        vector<string> res;
        if (s.size() <= 10) return res;
        int mask = 0x7ffffff, cur = 0;
        unordered_map<int, int> m;
        for (int i = 0; i < 9; ++i) {
            cur = (cur << 3) | (s[i] & 7);
        }
        for (int i = 9; i < s.size(); ++i) {
            cur = ((cur & mask) << 3) | (s[i] & 7);
            if (m.count(cur)) {
                if (m[cur] == 1) res.push_back(s.substr(i - 9, 10));
                ++m[cur]; 
            } else {
                m[cur] = 1;
            }
        }
        return res;
    }
};
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class Solution {
public:
    vector<string> findRepeatedDnaSequences(string s) {
        unordered_set<string> res;
        unordered_set<int> st;
        unordered_map<int, int> m{{'A', 0}, {'C', 1}, {'G', 2}, {'T', 3}};
        int cur = 0;
        for (int i = 0; i < 9; ++i) cur = cur << 2 | m[s[i]];
        for (int i = 9; i < s.size(); ++i) {
            cur = ((cur & 0x3ffff) << 2) | (m[s[i]]);
            if (st.count(cur)) res.insert(s.substr(i - 9, 10));
            else st.insert(cur);
        }
        return vector<string>(res.begin(), res.end());
    }
};

还有 格雷码 翻转位 两数相除等等

只出现一次的数

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class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int res = 0;
        for (auto num : nums)
            res ^= num;
        return res;
    }
};