STL 之accumulate,adjacent_difference,inner_product,partial_sum

accumulate,adjacent_difference,inner_product,partial_sum 这些算法都是数字算法，因此只能操作数字类型的数据。

头文件

#include <numeric>

声明：

#include <numeric>

template <class inputItr, class Type>

Type accumulate(inputItr first, inputItr last, Type init);

template <class inputItr, class Type, class binaryOperation>

Type accumulate(inputItr first, inputItr last, Type init,binaryOperation op);



template<class inputItr, class outputItr, class binaryOperation>

outputItr adjacent_difference(inputItr first,inputItr last, outputItr destFirst);

template<class inputItr, class outputItr>

outputItr adjacent_difference(inputItr first,inputItr last, outputItr destFirst,binaryOperation op);



template<class inputItr1, class inputItr2,class Type>

Type inner_product(inputItr1 first1,inputItr1 last1,inputItr2 first2,inputItr2 last2,Type init);

template<class inputItr1, class inputItr2,class Type, class binaryOperation1, class binaryOperation2>

Type inner_product(inputItr1 first1,inputItr1 last1,inputItr2 first2,inputItr2 last2,Type init,binaryOperation1 op1,binaryOperation2 op2);



template<class inputItr, class outputItr>

outputItr partial_sum(inputItr first,inputItr last,outputItr destFirst);

template<class inputItr, class outputItr, class binaryOperation>

outputItr partial_sum(inputItr first,inputItr last,outputItr destFirst,binaryOperation op);

inner_product : init = init op1 (elem op2 elem)

示例代码：

#include <iostream>

#include <list>

#include <string>

#include <iterator>

#include <vector>

#include <functional>

#include <algorithm>



#include <numeric>



using namespace std;



void print(vector<int> vList) {

ostream_iterator<int> screenOut(cout," ");

copy(vList.begin(),vList.end(),screenOut);

cout << endl;

}



int main() {

int list[8] = {1,2,3,4,5,6,7,8};

vector<int> vecList(list, list+8);

vector<int> newvList(8);

cout << "vecList:" << endl;

print(vecList);



int sum = accumulate(vecList.begin(),vecList.end(),0);

cout << "sum:" << sum << endl;



int product = accumulate(vecList.begin(),vecList.end(),1,multiplies<int>());

cout << "product:" << product << endl;



// adjacent_difference

adjacent_difference(vecList.begin(),vecList.end(),newvList.begin());

cout << "newvList:" << endl;

print(newvList);



adjacent_difference(vecList.begin(),vecList.end(),newvList.begin(),multiplies<int>());

cout << "newvList:" << endl;

print(newvList);



sum = inner_product(vecList.begin(),vecList.end(),newvList.begin(),0);

cout << "sum:" << sum << endl;

cout << "newvList:" << endl;

print(newvList);



sum = inner_product(vecList.begin(),vecList.end(),newvList.begin(),0,plus<int>(),minus<int>());

cout << "sum:" << sum << endl;

cout << "newvList:" << endl;

print(newvList);



partial_sum(vecList.begin(),vecList.end(),newvList.begin());

cout << "newvList:" << endl;

print(newvList);



partial_sum(vecList.begin(),vecList.end(),newvList.begin(),minus<int>());

cout << "newvList:" << endl;

print(newvList);

return 0;

}

运行结果：

vecList:

1 2 3 4 5 6 7 8

sum:36

product:40320

newvList:

1 1 1 1 1 1 1 1

newvList:

1 2 6 12 20 30 42 56

sum:1093

newvList:

1 2 6 12 20 30 42 56

sum:-133

newvList:

1 2 6 12 20 30 42 56

newvList:

1 3 6 10 15 21 28 36

newvList:

1 -1 -4 -8 -13 -19 -26 -34