程序员面试金典_2020_10_8

面试题 10.02. 变位词组

class Solution {
public:
    vector<vector<string>> groupAnagrams(vector<string>& strs) {
    int len=strs.size();
    map<string,vector<string>>m;
    for(int i=0;i<len;i++)
    {
        int l=strs[i].size();
        string tmp=strs[i];
        sort(tmp.begin(),tmp.end());     
        m[tmp].push_back(strs[i]);
    }
    vector<vector<string>>res;
    for(auto k=m.begin();k!=m.end();k++)
    {
        res.push_back(k->second);
    }
    return res;
    }
};

面试题 10.03. 搜索旋转数组

class Solution {
public:
    int search(vector<int>& arr, int target) {
   if(arr.empty()) return -1;
        int left = 0, right = arr.size()-1;
        while(left <= right){
            int mid = (left+right) >> 1;
            //左边有序
            if(arr[left] < arr[mid]){
                //目标值在左边
                if(arr[left] <= target && target <= arr[mid]) right = mid;
                else left = mid+1;
            }
            //右边有序
            else if(arr[left] > arr[mid]){
                //目标值在右边
                if(arr[mid] <= target && target <= arr[right] && arr[left] > arr[right]) left = mid;
                else right = mid-1;
            }
            //如果左值等于中值，可能是已经找到了目标，也可能是遇到了重复值
            else if(arr[left] == arr[mid]){
                //如果左值不等于目标，说明还没找到，需要逐一清理重复值。
                if(arr[left] != target) left++;
                else return left;
            }
        }
        return -1;
    }
};

面试题 10.05. 稀疏数组搜索

class Solution {
public:
    int findString(vector<string>& words, string s) {
    int left=0,right=words.size()-1;
    while(left<=right)
    {
        int mid=(left+right)/2;
        int tmp=mid;
        while(mid>=left&&words[mid]=="")
        {
            mid-=1;
        }
        if(words[mid]==s)
        {
            return mid;
        }
        else if(words[mid]>s)
        {
            right=mid-1;
        }
        else left=tmp+1;
    }
    return -1;
    }
};

面试题 10.09. 排序矩阵查找

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
   
   
   if(matrix.empty()||matrix[0].empty()) return false;
   int m=matrix.size(),n=matrix[0].size();
   int i=0,j=n-1;
   while(i<m&&j>=0)
   {
       if(matrix[i][j]==target) return true;
       else if(matrix[i][j]>target)
       {
           j--;
       }
       else if(matrix[i][j]<target)
       {
           i++;
       }
   }
   return false;
    }
};

面试题 10.10. 数字流的秩

class StreamRank {
public:
map<int,int>tmp;
    StreamRank() {

    }
    
    void track(int x) {
   tmp[x]++;
    }
    
    int getRankOfNumber(int x) {
    int res=0;
    for(auto it=tmp.begin();it!=tmp.end();it++)
    {
        if(it->first<=x)
        res+=it->second;
    }
    return res;

    }
};