printf() and scanf() format
printf("%d", n);
FORMAT ARGUMENT TYPE
%d, %i int decimal
%lld long long
%llu unsigned long long
%u unsigned int
%x unsigned int hexadecimal
%#x unsigned int hexadecimal with prefix 0x
%f double
%Lf long double
%c char to print a character
%s char * string (character array ended with '\0')
scanf("%d", &n);
FORMAT ARGUMENT TYPE
%d int * &n, store the input integer in n
%ld long *
%lld long long *
%u unsigned int *
%f float * read float
%lf double * read double
%Lf long double * read long double
%c char * read 3 characters %3c
%s char * read a string until whitespace
%n int * with %s, to get string length
char a[100]; int len;
scanf("%s%n", a, &len);
len will have the string length
Frequently used functions
#include <string.h>
char str[10];
scanf("%s", str);
to get the string length using strlen(str)
#include <ctype.h>
isspace(ch), islower(ch), isupper(ch), isdigit(ch)
isalpha(ch), toupper(ch), tolower(ch)
To create a 5-by-5 two-dimensional array, we need to write
int a[5][5];
It will be indexed as follows:
|
a[0][0] |
a[0][1] |
a[0][2] |
a[0][3] |
a[0][4] |
|
a[1][0] |
a[1][1] |
a[1][2] |
a[1][3] |
a[1][4] |
|
a[2][0] |
a[2][1] |
a[2][2] |
a[2][3] |
a[2][4] |
|
a[3][0] |
a[3][1] |
a[3][2] |
a[3][3] |
a[3][4] |
|
a[4][0] |
a[4][1] |
a[4][2] |
a[4][3] |
a[4][4] |
How to read the following data?
1 2 3 4 5 e
#include <stdio.h>
int main(void)
{
int x;
while (scanf("%d", &x) == 1) {
printf("x=%d\n", x);
}
return 0;
}
How to read the following data?
2
L 5 2
D 5 3
#include <stdio.h>
int main(void)
{
char ch;
int i, n, row, col;
scanf("%d", &n);
for (i=0; i<n; i++) {
while(getchar()!='\n');
scanf("%c%d%d", &ch, &row, &col);
}
return 0;
}
Using for loops to print a two-dimensional array
for(i = 0; i < row; i++) {
for (j = 0; j < col; j++) {
printf("%5d", A[i][j]);
}
printf("\n");
}
logical and comparison operators operators:
! && || == != > < >= <=
arithmetic operators:
+ - * / %
bitwise operators:
& | ^ << >> ~
int strcmp(const char *lhs, const char *rhs);
int strcat(const char *lhs, const char *rhs);
int strcpy(const char *lhs, const char *rhs);
How to avoid common errors and how to debug for OJ
1. Put the arrays in the 'global' area. Set their size bigger than required. Avoid using variable-length arrays (e.g. int arr[n];). Keep the array size fix (e.g., int arr[1000];).
2. After writing the code for reading input data, you may print out the data to check if your code reads them correctly. Do not proceed to write subsequent code before you confirm that.
3. If your program crashes, usually it is caused by memory related errors. Check the ranges of for-loops to see if your code attempts to read or write the elements out of the arrays' boundary.
Note : If you are using visual studio, add #pragma warning(disable:4996) in the first line so that you can use scanf on your local machine.