lower_bound upper bound

#include <iostream>using namespace std;int my_lower_bound(int *array, int size, int key){int first = 0, last = size - 1;int middle, pos = 0;       //需要用pos记录第一个大于等于key的元素位置while (first < last){middle = (first + last) / 2;if (array[middle] < key){      //若中位数的值小于key的值，我们要在右边子序列中查找，这时候pos可能是右边子序列的第一个first = middle + 1;pos = first;}else{last = middle;           //若中位数的值大于等于key，我们要在左边子序列查找，但有可能middle处就是最终位置，所以我们不移动last,pos = last;              //而是让first不断逼近last。}}return pos;}int stl_ower_bound(int *array, int size, int key){int first = 0, middle;int half, len;len = size;while (len > 0) {half = len >> 1;middle = first + half;if (array[middle] < key) {first = middle + 1;len = len - half - 1;       //在右边子序列中查找}elselen = half;            //在左边子序列（包含middle）中查找}return first;}int lower_bound(int * a, int length, int target)// find the first one larger than //target{int pb = 0;int pe = length - 1;int mid = 0;int pos = 0;while (pb<pe){mid = (pb + pe) / 2;if (a[mid]<target){pb = mid + 1;pos = pb;}else{//a[mid]<=target ; this means a[mid] is not the answer to return;pe = mid;pos = pe;}}// return a[pos];return pos;}int low_up_bound(int * a, int length, int key, bool flag){int pb = 0;int pe = length - 1;int mid = 0;int pos = 0;while ( pb < pe ){mid = (pb + pe) / 2;if (a[mid] == key){if (flag){//upper_bound;pb = mid + 1;//pb = mid;pos = pb;}else{//lower_bound;pe = mid;pos = pe;}}elseif (a[mid]>key){pe = mid;pos = pe;}else{//a[mid]<keypb = mid + 1;pos = pb;}}return pos;}int main(){cout << "Hello World" << endl;//int a[7] = { 2, 4, 4, 4, 4, 8, 10 };int a[7] = { 1, 2, 3, 4, 5, 6, 7 };int length = sizeof(a) / sizeof(int);cout << lower_bound(a, length, 4) << endl;cout << stl_ower_bound(a, length, 4) << endl;cout << my_lower_bound(a, length, 4) << endl;cout << low_up_bound(a, length, 4, true) << endl;cout << low_up_bound(a, length, 4, false) << endl;return 0;}