二分查找:
- 要求:数组的元素必须是有序的
- 思想:每次都查找中间的元素,比较大小就能减少一半元素
#include <iostream>
using namespace std;
int getIndex(int *arr, unsigned int arrLength, int num);
int main()
{
int arrayLength = 6;
int array[arrayLength] = {10,20,21,30,35,60};
for (int i = 0; i < arrayLength; i++)
{
cout << array[i] << " ";
}
cout << endl;
int index = getIndex(array, arrayLength, 60);
cout << "findIndex: " << index << endl;
system("pause");
return 0;
}
int getIndex(int *arr, unsigned int arrLength, int num)
{
int minIndex = 0;
int maxIndex = arrLength-1;
int centerIndex = (minIndex+maxIndex)/2;
while (minIndex <= maxIndex)
{
if(num == arr[centerIndex]) //你要找的元素刚好与中间索引的元素一致
{
return centerIndex;
}
else if (num > arr[centerIndex]) //你要找的元素大于中间索引元素
{
minIndex = centerIndex+1;
}
else if (num < arr[centerIndex]) //你要找的元素小于于中间索引元素
{
maxIndex = centerIndex-1;
}
//重新计算中间索引
centerIndex = (minIndex+maxIndex)/2;
}
return -1; //未查找到
}