找到一个乱序数组排序后某一特定数值首次和末次出现的位置

来源：互联网发布：上海编程培训班编辑：程序博客网时间：2024/04/30 15:30

不多说，上代码，我的思路是利用快速排序，进行数组排序，而后利用二分查找方法，进行快速定位

int intArray[]={12,451,0,5,45,15,78,23,54,76,451};void QuickSort(int* a,int low,int high){if(NULL==a){return;}if(low>=high){return ;}int first=low,last=high;int key=a[low];while(first<last){while(first<last&&key<=a[last]){last--;}a[first]=a[last];while(first<last&&key>=a[first]){first++;}a[last]=a[first];}a[first]=key;QuickSort(a,low,first-1);QuickSort(a,first+1,high);}int getFirstPos(int*a,int value,int length){         if(NULL==a) return;        int low=0,high=length-1;int mid=(low+high)/2;int nPos=-1;while(low<=high){mid=(low+high)/2;if(value<a[mid]){high=mid-1;}else if(value==a[mid]){nPos=mid;high=mid-1;}else{low=mid+1;}}return nPos;}int getLastPos(int*a,int value,int length){        if(NULL==a) return;        int low=0,high=length-1;int mid=(low+high)/2;int nPos=-1;while(low<=high){mid=(low+high)/2;if(value<a[mid]){high=mid-1;}else if(value==a[mid]){nPos=mid;low=mid+1;}else{low=mid+1;}}return nPos;}int main(){QuickSort(intArray,0,10);cout<<451<<"第一次出现的位置是："<<getFirstPos(intArray,451,11)<<endl;cout<<451<<"最后一次出现的位置是："<<getLastPos(intArray,451,11)<<endl;}

经测试结果正确

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