Rounding Floating Point Number To two Decimal Places in C and C++

How to round off a floating point value to two places. For example, 5.567 should become 5.57 and 5.534 should become 5.53

First Method:- Using Float precision

C

#include <stdio.h>
int main()
{
    float var = 37.66666;

    // Directly print the number with .2f precision
    printf("%.2f", var);
    return 0;
}

C++

#include<bits/stdc++.h>
using namespace std;

int main()
{
    float var = 37.66666;

    // Directly print the number with .2f precision
    cout << fixed << setprecision(2) << var;
    return 0;
}

// This code is contributed by shivanisinghss2110

Output

37.67

Time Complexity: O(1), as the execution time does not depend on the size of the input.

Space Complexity: O(1), as it only uses a fixed amount of memory to store a single float variable and does not allocate any dynamic memory.

Second Method: Using integer typecast If we are in Function then how return two decimal point value

C++

#include <iostream>
using namespace std;
float round(float var)
{
    // 37.66666 * 100 =3766.66
    // 3766.66 + .5 =3767.16    for rounding off value
    // then type cast to int so value is 3767
    // then divided by 100 so the value converted into 37.67
    float value = (int)(var * 100 + .5);
    return (float)value / 100;
}

int main()
{
    float var = 37.66666;
    cout << round(var);
    return 0;
}

Output:
37.67

Time complexity:
The round function only performs a few basic arithmetic operations, so its time complexity is constant or O(1). 

Space complexity:
The round function creates a single float variable named value, so its space complexity is constant or O(1).

Third Method: using sprintf() and sscanf() 

C++

#include <iostream>
using namespace std;
float round(float var)
{
    // we use array of chars to store number
    // as a string.
    char str[40];

    // Print in string the value of var
    // with two decimal point
    sprintf(str, "%.2f", var);

    // scan string value in var
    sscanf(str, "%f", &var);

    return var;
}

int main()
{
    float var = 37.66666;
    cout << round(var);
    return 0;
}

Output:
37.67

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