Nested Loops in C++ with Examples
Last Updated :
12 Jul, 2025
Nested loop means a
loop statement inside another loop statement. That is why nested loops are also called as "
loop inside loop".
Syntax for Nested For loop:
for ( initialization; condition; increment ) {
for ( initialization; condition; increment ) {
// statement of inside loop
}
// statement of outer loop
}
Syntax for Nested While loop:
while(condition) {
while(condition) {
// statement of inside loop
}
// statement of outer loop
}
Syntax for Nested Do-While loop:
do{
do{
// statement of inside loop
}while(condition);
// statement of outer loop
}while(condition);
Note: There is no rule that a loop must be nested inside its own type. In fact, there can be any type of loop nested inside any type and to any level.
Syntax:
do{
while(condition) {
for ( initialization; condition; increment ) {
// statement of inside for loop
}
// statement of inside while loop
}
// statement of outer do-while loop
}while(condition);
Below are some examples to demonstrate the use of Nested Loops:
Example 1: Below program uses a nested for loop to print a 2D matrix of 3x3.
CPP
// C++ program that uses nested for loop
// to print a 2D matrix
#include <bits/stdc++.h>
using namespace std;
#define ROW 3
#define COL 3
// Driver program
int main()
{
int i, j;
// Declare the matrix
int matrix[ROW][COL] = { { 1, 2, 3 },
{ 4, 5, 6 },
{ 7, 8, 9 } };
cout << "Given matrix is \n";
// Print the matrix using nested loops
for (i = 0; i < ROW; i++) {
for (j = 0; j < COL; j++)
cout << matrix[i][j];
cout << "\n";
}
return 0;
}
Output:
Given matrix is
123
456
789
Example 2: Below program uses a nested for loop to print all prime factors of a number.
CPP
// C++ Program to print all prime factors
// of a number using nested loop
#include <bits/stdc++.h>
using namespace std;
// A function to print all prime factors of a given number n
void primeFactors(int n)
{
// Print the number of 2s that divide n
while (n % 2 == 0) {
cout << 2;
n = n / 2;
}
// n must be odd at this point. So we can skip
// one element (Note i = i +2)
for (int i = 3; i <= sqrt(n); i = i + 2) {
// While i divides n, print i and divide n
while (n % i == 0) {
cout << i;
n = n / i;
}
}
// This condition is to handle the case when n
// is a prime number greater than 2
if (n > 2)
cout << n;
}
/* Driver program to test above function */
int main()
{
int n = 315;
primeFactors(n);
return 0;
}
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