Data Structure -- algorithm (016) (input integer n, calculate the number of times 1 appears in the decimal representation of the n integers from 1 to n and)

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Question:

Enter an integer n to calculate the number of times 1 appears and

Question Analysis:

I. In fact, the problem can be converted to the number of occurrences of 1 in a number, which involves basic remainder and Division operations.

Algorithm Implementation:

# Include

 
  
/*** Calculate the number of digits @ digit contained in the integer @ m */int count_digit_num (int m, int digit) {int count = 0; while (m) {if (m % 10 = digit) count ++; m = m/10;} return count;} int count_digit_one (int m) {int I = 0; int count = 0; for (; I <= m; I ++) {count + = count_digit_num (I, 1) ;}return count ;} int main (int argc, char * argv []) {int m = atoi (argv [1]); printf ("% d -----> % d \ n", m, count_digit_one (m ));}