std :: replace
将new_value分配给与old_value比较的[first，last)范围内的所有元素。该函数使用运算符==将各个元素与old_value进行比较
函数模板：
void replace (ForwardIterator first,
ForwardIterator last,
const T& old_value,
const T& new_value)
first, last :
Forward iterators to the initial and final positions
in a sequence of elelments.
old_value : Value to be replaced.
new_value : Replacement value.
返回值：
此函数不返回任何值。如果找到需要替换的元素，则元素
更换，否则保持不变。
例子：
Input : 10 20 30 30 20 10 10 20
Output : 10 99 30 30 99 10 10 99
// Replaced value 20 in vector to 99.
Input : 3 5 7 8 9 5 4
Output : 3 5 7 12 9 5 4
// Replaced value 8 by 12.
CPP
// CPP program to find and replace the value
// with another value in array
// using std::replace
#include
using namespace std;
// Driver code
int main()
{
int arr[] = { 10, 20, 30, 30, 20, 10, 10, 20 };
int n = sizeof(arr) / sizeof(arr[0]);
// variable containing the old and new values
int old_val = 20, new_val = 99;
// print old array
cout << "Original Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
// Function used to replace the values
replace(arr, arr + n, old_val, new_val);
// new array after using std::replace
cout << "New Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
return 0;
} CPP
// CPP code to find all the elements that are odd
// and replace them with 0.
// using std::replace_if
#include
using namespace std;
// Function that is used in std::replace_if
// If number is odd return 1, else 0
// 1 (True) means replace the number
// 0 (False) means does not replace
bool IsOdd(int i)
{
return ((i % 2) == 1);
}
// Driver code
int main()
{
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int n = sizeof(arr) / sizeof(arr[0]);
// print old array
cout << "Original Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
// replacement value
int new_val = 0;
// replace_if function
replace_if(arr, arr + n, IsOdd, new_val);
// new array after using std::replace
cout << "New Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
return 0;
} 输出
Original Array: 10 20 30 30 20 10 10 20
New Array: 10 99 30 30 99 10 10 99
std :: replace_if
将new_value分配给pred返回true的[first，last)范围内的所有元素。
函数模板：
void replace_if (ForwardIterator first, ForwardIterator last,
UnaryPredicate pred, const T& new_value)
first, last : Forward iterators to the initial and final positions
in a sequence of elelments.
pred : Unary function that accepts an element in the range as argument, and
returns a value convertible to bool.The returned value indicate whether
the element is to be replaced (if true, it is replaced).
The function shall not modify its argument.
old_value : Value to be replaced.
new_value : Replacement value.
例子：
Input : 1 2 3 4 5 6 7 8 9 10
Output : 0 2 0 4 0 6 0 8 0 10
// Replaced all odd values to 0.
Input : 10 20 30 30 20 10 10 20
Output : 10 4 30 30 4 10 10 4
// Replaced all number divisible by 4 to 4.
CPP
// CPP code to find all the elements that are odd
// and replace them with 0.
// using std::replace_if
#include
using namespace std;
// Function that is used in std::replace_if
// If number is odd return 1, else 0
// 1 (True) means replace the number
// 0 (False) means does not replace
bool IsOdd(int i)
{
return ((i % 2) == 1);
}
// Driver code
int main()
{
int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int n = sizeof(arr) / sizeof(arr[0]);
// print old array
cout << "Original Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
// replacement value
int new_val = 0;
// replace_if function
replace_if(arr, arr + n, IsOdd, new_val);
// new array after using std::replace
cout << "New Array:";
for (int i = 0; i < n; i++)
cout << ' ' << arr[i];
cout << '\n';
return 0;
}
输出
Original Array: 1 2 3 4 5 6 7 8 9 10
New Array: 0 2 0 4 0 6 0 8 0 10
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