剑指offer 编程题（27）：数组中出现次数统计

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题目描述

数组中有一个数字出现的次数超过数组长度的一半，请找出这个数字。例如输入一个长度为9的数组{1,2,3,2,2,2,5,4,2}。由于数字2在数组中出现了5次，超过数组长度的一半，因此输出2。如果不存在则输出0

class Solution {public:    int MoreThanHalfNum_Solution(vector<int> numbers) {        if(numbers.size() == 0)            return 0;        map<int,int> countmap;        int size = numbers.size()/2;        for(int i=0; i<numbers.size(); ++i)        {            countmap[ numbers[i] ]++;            if(countmap[ numbers[i] ] > size)                return numbers[i];        }        return 0;    }};

扩展一：统计数组中出现次数最多的数字，返回最多次数。

class Solution {public:    int MoreThanHalfNum_Solution(vector<int> numbers) {        if (numbers.size() == 0)            return 0;        int maxcount = 0;        map<int, int> countmap;        //int size = numbers.size() / 2;        for (int i = 0; i < numbers.size(); ++i)        {            countmap[numbers[i]]++;            if (countmap[numbers[i]] > maxcount)                maxcount = countmap[numbers[i]];        }        return maxcount;    }};

扩展二：统计数组中出现次数最多的数字，返回最多次数的那个数字。

class Solution {public:    int MoreThanHalfNum_Solution(vector<int> numbers) {        if (numbers.size() == 0)            return 0;        int maxcount = 0;        int maxnumber = 0;        map<int, int> countmap;        //int size = numbers.size() / 2;        for (int i = 0; i < numbers.size(); ++i)        {            countmap[numbers[i]]++;            if (countmap[numbers[i]] > maxcount)            {                maxcount = countmap[numbers[i]];                maxnumber = numbers[i];            }        }        return maxnumber;    }};

扩展三：统计数组中出现次数，返回第二多次数的那个数字。

class Solution {public:    int MoreThanHalfNum_Solution(vector<int> numbers) {        if (numbers.size() == 0)            return 0;        int maxcount = 0;        int maxnumber = 0;        int seccount = 0;        int secnumber = 0;        map<int, int> countmap;        int size = numbers.size() / 2;        for (int i = 0; i < numbers.size(); ++i)        {            countmap[numbers[i]]++;        }        for (int i = 0; i < countmap.size(); ++i)        {            if (countmap[numbers[i]] > maxcount)            {                seccount = maxcount;                secnumber = maxnumber;                maxcount = countmap[numbers[i]];                maxnumber = numbers[i];            }            else if(countmap[numbers[i]] > seccount && countmap[numbers[i]] <= maxcount)            {                seccount = countmap[numbers[i]];                secnumber = numbers[i];            }        }        cout << "最多次数的数字是：" << maxnumber << "出现了" << maxcount << "次"<<endl;        cout<< "第二多次数是：" << secnumber << "出现了" << seccount << "次" << endl;        return secnumber;    }};

扩展四：统计字符串中出现次数，返回出现最多次数的那个字符。‘

#include<iostream>  #include<string>  #include<stdlib.h>using namespace std;int main(){    string str;    cout << "input some text:" << endl;    getline(cin, str);    int maxcount = 0;    string maxstring;    int cnt[256] = {};    for (int i = 0; i<str.size(); i++)        cnt[(int)str[i]]++;    for (int i = 0; i<256; i++)//输出字符出现次数      {        if (cnt[i] != 0)            cout << (char)i << ':' << cnt[i] << endl;        if (cnt[i] > maxcount)        {            maxcount = cnt[i];            maxstring = (char)i;        }    }    cout <<"出现次数最多的字符是"<< maxstring << "出现了"<<maxcount<<"次" << endl;    system("pause");}

class Solution {public:    string MoreThanHalfNum_Solution(string str)     {        int maxcount = 0;        string maxstring;        int cnt[256] = {};        for (int i = 0; i<str.size(); i++)            cnt[(int)str[i]]++;        for (int i = 0; i<256; i++)//输出字符出现次数          {            if (cnt[i] != 0)                cout << (char)i << ':' << cnt[i] << endl;            if (cnt[i] > maxcount)            {                maxcount = cnt[i];                maxstring = (char)i;            }        }        cout << "出现次数最多的字符是" << maxstring << "出现了" << maxcount << "次" << endl;        return maxstring;    }};

#define _CRT_SECURE_NO_WARNINGS 1  #include<stdio.h>  #include<stdlib.h>  #include<assert.h>  #include<string>#include<iostream>#include<vector>#include<map>using namespace std;class Solution {public:    string MoreThanHalfNum_Solution(string str)     {        int maxcount = 0;        string maxstring;        map<char, int> cnt;        for (int i = 0; i<str.size(); i++)            cnt[str[i]]++;        for (int i = 0; i<cnt.size(); i++)//输出字符出现次数          {            if (cnt[i] != 0)                cout << (char)i << ':' << cnt[i] << endl;            if (cnt[i] > maxcount)            {                maxcount = cnt[i];                maxstring = (char)i;            }        }        cout << "出现次数最多的字符是" << maxstring << "出现了" << maxcount << "次" << endl;        return maxstring;    }};int main(){    string b = "aaaaaabbbbbbbbbccccddddddddddddddddddddd";    Solution s;    string count;    count = s.MoreThanHalfNum_Solution(b);    cout << count << endl;    system("pause");    return 0;}

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