学步园

Syntax:

    #include <numeric>
    output_iterator adjacent_difference( input_iterator start, input_iterator end, output_iterator result );
    output_iterator adjacent_difference( input_iterator start, input_iterator end, output_iterator result, BinaryFunction f );

The adjacent_difference() function calculates the differences between adjacent elements in the range [start,end) and stores the result starting at result. (Specifically, the element at start will be copied to result; and then the difference between the element at start + i and start + (i-1) will be stored at result + i.)

If a binary function f is given, it is used instead of the - operator to compute the differences. adjacent_difference() runs in linear time.

Following example displays the differences between adjacent elements in a vector.

这个算法的意思是，计算一个数组里面的元素的“差别”，第一个元素呢，不变，然后用第i（i>=2）个元素减去前面那个值，把所得的结果存在第i个位置。废话少说，看源码演示：

#include <algorithm><br /> #include <iostream><br /> #include <iterator><br /> #include <numeric><br /> #include <vector><br /> using namespace std;<br /> int main()<br /> {<br /> int a[]={10,3,6,4,7,4,6,4,3,891};<br /> vector<int> v(a,a+sizeof(a)/sizeof(a[0]));<br /> copy(v.begin(), v.end(), ostream_iterator<int>(cout, " ")); // display elements of v<br /> cout << endl;<br /> adjacent_difference(v.begin(), v.end(), ostream_iterator<int>(cout, " ")); // display all differences between elements<br /> cout<<endl;<br /> return 0;<br /> }

毫无疑问，When run, this code displays the following output:

10 3 6 4 7 4 6 4 3 891
10 -7 3 -2 3 -3 2 -2 -1 888