Create armstrong.c

algorithms/C/maths/armstrong.c

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+// This program is used to check if a given no is armstrong number or not in C
+// an armstrong number is a number that equals the sum of its digits, each raised to a power.
+// power is the number of digits in the number eg. 123 has three digits, so power will be 3.
+
+#include<stdio.h>
+#include<math.h>
+
+int main(){                             //main function
+    int num,digit=0,temp,sum=0;         //define variables
+    printf("enter the number: ");       
+    scanf("%d",&num);                   //taking inputs
+    temp=num;
+    while(temp>0){
+        digit++;                        //counting number of digits in the input number
+        temp=temp/10;
+    }
+    printf("Number of digits: %d\n",digit);
+    temp=num;
+    while(temp>0){
+        sum=sum+ (int)(pow(temp%10, digit)+0.5);    // checking the armstrong property of the number
+        temp/=10;                                   // we extract a digit from number using (temp%10) then 
+    }                                               // raise that digit to number of digits in the number using pow function
+                                                    // (pow()+0.5) is used to increase precision
+    printf("Sum of powered digits: %d\n",sum);
+    if(num==sum){                                   //checking if the new number is equal to the input number
+        printf("Armstrong");
+    }
+    else{
+        printf("Not Armstrong");
+    }
+    return 0;
+}
+
+//         Input        ||       Output
+//          153         ||      Armstrong
+//          371         ||      Armstrong
+//          1634        ||      Armstrong
+//          123         ||      Not Armstrong
+
+// This program has time complexity of O(N).