将输入复制到其输出，将一个或多个空格的每个字符串替换为一个空格。

#include <stdio.h>

int main(void){
    int c, blank_recieved = 0;
    printf("Input some characters, when you finishes, press Ctrl+D./n");

    while ((c = getchar()) != EOF){
        if (c == ' ') {
            if (!blank_recieved) {
                blank_recieved = 1;
                putchar(c);
            }
        } else {
            blank_recieved = 0;
            putchar(c);
        }
}
    return 0;
}