别忘考虑已经大写了的情况

#include <stdio.h>
#include <stdbool.h>
#include <math.h>
#include <string.h>

int main(void) {
    char s[100];
    while(gets(s)!=NULL){
        for(int i=0;i<strlen(s);i++){
            if(i==0&&(s[i]>='a'&&s[i]<='z')) s[i] = s[i]-32;
            else if(s[i-1]==' '&&(s[i]>='a'&&s[i]<='z')) s[i] = s[i]-32;
            else if(s[i-1]=='\t'&&(s[i]>='a'&&s[i]<='z')) s[i] = s[i]-32;
            else if(s[i-1]=='\n'&&(s[i]>='a'&&s[i]<='z')) s[i] = s[i]-32;
            else if(s[i-1]=='\r'&&(s[i]>='a'&&s[i]<='z')) s[i] = s[i]-32;
        }
        puts(s);
        printf("\n");
    }
    return 0;
}