Password validator code, but segmentation error occurs.

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int valid_char(char* a, int b);
int valid_num(char* a, int b);
int valid_space(char* a, int b);
int validoption(char* a);

int main() {
char* pw;
    printf("Input password :");
    scanf("%[^\n]s",pw);


    if (strlen(pw) < 5 || strlen(pw) > 10){
        printf("Invalid password");
        return 0;
    }
    if (validoption(pw) == 0)
        printf("Valid password");
    else printf("Invalid password");
    return 0;
}

int valid_char(char* a, int b) {
    char aa[10];
    sprintf(aa, "%s", a);
    int i;
    for (i = 0; i < b; i++) {
        if (aa[i] >= 33 && aa[i] <= 47)
            return 1;
        else if (aa[i] >= 58 && aa[i] <= 64)
            return 1;
        else if (aa[i] >= 123 && aa[i] < 126)
            return 1;
    }
    return -1;
}


int valid_num(char* a, int b) {
    char aa[10];
    sprintf(aa, "%s", a);
    int i;
    for (i = 0; i < b; i++) {
        if (aa[i] >= 48 && aa[i] <= 57)
            return 1;
        else return 0;
    }
    return -1;
}
int valid_space(char* a, int b) {
    char aa[10];
    sprintf(aa, "%s", a);
    int i;
    for (i = 0; i < b; i++) {
        if (aa[i] == 32)
            return 0;
    }
    return 1;

}
int validoption(char* a) {
    int sum = valid_char(a, strlen(a)) + valid_num(a, strlen(a)) + valid_space(a, strlen(a));
    if (sum == 3)
        return 0;
    else return -1;
}