sorting string

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

//remove redundant spaces in a string s

void removeRedSpaces(char s[]) {
        int n, low, up, i, j; char x[100];
        n = strlen(s);
        i = 0; j = n - 1;
        while(i < n && s[i] == ' ') i++;
        low = i;
        while(j > 0 && s[j] == ' ') j--;
        up = j;
        if(low > up) {
                strcpy(s, "");
                return;
        }
        strcpy(x, "");
        i = low; j = 0;
        while(i <= up) {
                while(i < up && s[i] == ' ') i++;
                while(i <= up && s[i] != ' ') x[j++] = s[i++];
                if(i <= up) x[j++] = ' ';
        }
        x[j] = '\0';
        strcpy(s,x);
}
void split( char s[], char out[][30], int &length) //tach cac tu trong 1 chuoi
{
        removeRedSpaces(s);
        int i = 0, j, k = 0;
        while ( i < strlen(s))
        {
                for ( j = i; s[j] != '\0' && s[j] != ' '; j ++)

                        out[ k ][ j - i ] = s[j];
                        out[ k ][ j - i ] = '\0';
                        i = j + 1;
                        k++;
        }
        length = k;
}

//Enter data for a string s
void input(char s[]) {
        printf("Enter a string s = ");
        fflush(stdin);
        gets(s);
}

//Display a string s
void display(char s[]) {
        printf("%s\n",s);
}

void fun(char s[]) {
        int i, j, n;
        char x[100][30], temp[30];
        split(s, x, n);
        for (i = n - 5; i < n ; i++)
                for (j = i + 1; j < n; j++)
                        if (strcmp(x[i],x[j]) > 0)
                                { //doi cho
                                        strcpy(temp,x[i]);
                                        strcpy(x[i],x[j]);
                                        strcpy(x[j],temp);
                                }

        // rebuild
        int length = strlen(s);
        strcpy(s, "");
        for (i = 0; i < n; ++i) {
                strcat(s, x[i]);
                strcat(s, " ");
        }
        s[length] = '\0';
}

int main()
{
        system("cls");
        printf("\nTEST Q5 (2 marks):\n");
        char s[100];
        input(s);
        printf("\nThe original string:\n");
        display(s);
        printf("\nThe string after processing:\n");
        fun(s);
        display(s);
        //==THE OUTPUT AFTER THIS LINE WILL BE USED TO MARK YOUR PROGRAM==
        printf("\nOUTPUT:\n");
        display(s);
        printf("\n");
        system ("pause");
        return(0);
}