剑指offer-面试题29 找到数组中出现次数超过一半的数字-1

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//方法一: 找出排序在中间的那个数字. 但是不是先排序,而是只要找到排在中间的数字就行.#include<iostream>using namespace std;void Swap(int &a, int &b){    int temp = a;    a = b;    b = temp;}//和快排类似, 找一个枢纽元,把小于枢纽元的数放在枢纽元左边, 返回枢纽元的位置int Partion(int *nArray, int nBegin, int nEnd){    if(nArray == NULL|| nBegin <0 || nEnd<0)        throw exception("ERROR");    int nPivot = nArray[nBegin];  //枢纽元    int nLeft = nBegin;    int nRight = nEnd;    while(nLeft != nRight)    {        while(nArray[nRight]>=nPivot && nLeft < nRight)            --nRight;        while(nArray[nLeft]<=nPivot && nLeft < nRight)            ++nLeft;        if(nLeft<nRight)        {            Swap(nArray[nLeft], nArray[nRight]);        }    }    Swap(nArray[nBegin], nArray[nLeft]);    return nLeft;}int FindMoreThanHalfNum(int *nArray, int nLength){    if(nArray == NULL || nLength <= 0)        throw exception("ERROR");    int nMiddle = nLength>>1;    int nBegin = 0;    int nEnd = nLength-1;    //找出排在中间的那个数的值就是.    int nNum = Partion(nArray, nBegin, nEnd);    while(nNum != nMiddle)    {        if(nNum > nMiddle)        {            nNum = Partion(nArray, nBegin, nNum-1);        }        else        {            nNum = Partion(nArray, nNum+1, nEnd);        }    }    return nArray[nNum];    /**    *省略检查这个数是不是超过数组一半 的代码    */}int main(){    int a[] = {0, 1, 2, 2,2,2,2,2,2, 3,3,3,3,3,3,3,3,3,3,3,3,3,4,5,6};    cout<<FindMoreThanHalfNum(a, 25);}//方法二:那个数字的出现次数比其他所有数字次数和要多,保存两个值,一个是数字,一个是次数,本次和上次不同数字则次数减一,相同则加1,如果次数为0,则保存此次的数字,最后的那个数字一定是想要的.#include<iostream>using namespace std; int FindMoreThanHalfNum(int * nArray, int nLength) {     if(nArray == NULL || nLength <=0)         throw exception("ERROR");     int nNum = nArray[0];     int nCount = 1;     for(int i = 1; i < nLength; ++i)     {         if(nArray[i] == nNum)             ++nCount;         else         {             --nCount;             if(!nCount)             {                 nNum = nArray[i];                 ++nCount;             }         }     }     //省略总次数检查     return nNum; }int main(){    int a[] = {0, 1, 2, 2,2,2,2,2,2, 3,3,3,3,3,3,3,3,3,3,3,3,3,4,5,6};    cout<<FindMoreThanHalfNum(a, 25)<<endl;}
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