函数upper_bound()返回的在前闭后开区间查找的关键字的上界，如一个数组number序列1,2,2,4.upper_bound(2)后，返回的位置是3（下标）也就是4所在的位置,同样，如果插入元素大于数组中全部元素，返回的是last。（注意：此时数组下标越界！！）
返回查找元素的最后一个可安插位置，也就是“元素值>查找值”的第一个元素的位置
测试代码如下：
#include <iostream> #include <algorithm> #include <functional> #include <vector> using namespace std; void main() { const int VECTOR_SIZE = 8 ; // Define a template class vector of int typedef vector<int, allocator<int> > IntVector ; //Define an iterator for template class vector of strings typedef IntVector::iterator IntVectorIt ; IntVector Numbers(VECTOR_SIZE) ; IntVectorIt start, end, it, location, location1; // Initialize vector Numbers Numbers[0] = 4 ; Numbers[1] = 10; Numbers[2] = 10 ; Numbers[3] = 30 ; Numbers[4] = 69 ; Numbers[5] = 70 ; Numbers[6] = 96 ; Numbers[7] = 100; start = Numbers.begin() ; // location of first // element of Numbers end = Numbers.end() ; // one past the location // last element of Numbers // print content of Numbers cout << "Numbers { " ; for(it = start; it != end; it++) cout << *it << " " ; cout << " }\n" << endl ; //return the last location at which 10 can be inserted // in Numbers location = lower_bound(start, end, 9) ; location1 = upper_bound(start, end, 10) ; cout << "Element 10 can be inserted at index " << location - start<< endl ; cout << "Element 10 can be inserted at index " << location1 - start<< endl ; }