Thread: A little help with string manipulation

Basically, what I'm trying to do is take a line of text from the user as input, then spew it back, but with "I am" replaced with "You are". There are a few printf's in here that are just there to show me what my own program is doing, for debugging purposes, but I can't seem to get this code working with more than one "I am" in the input, even though it should. I know there are some things I could be doing more efficiently, so if you see them, please point them out.

Please have a look and tell me what you think I should change. Thanks in advance

Code:

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

char    recent[99];

int main(void) {
    int     i, q[3], w = 0, x, b[3];
    
    /* Set arrays to zero */
    for (i = 0; i <= 99; ++i) {
        recent[i] = -1;
    }
    for (i = 0; i <= 3; ++i) {
        q[i] = -1;
        b[i] = 0;
    }
    
    /* Get a string from the user, then check for 'I' */
    fgets(recent, 100, stdin);
    recent[(strlen(recent) - 1)] == '\0';
    for (i = 0; i <= 99; ++i) {
        if (recent[i] == 'I') {
            q[w] = i;
            ++w;
        }
    }
    
    /* Check to see if 'I' is followed by ' am' */
    for (i = 0; i <= 3; ++i) {
        if (recent[(q[i] + 1)] == ' ') {
            if (recent[(q[i] + 2)] == 'a') {
                if (recent[(q[i] + 3)] == 'm') {
                    printf("\nq[%i] is an \"I am\" statement.", i);
                    b[i] = 1;
                }
            }
        }
    }
    
    /* Replace 'I am' with 'You are' */
    for (i = 0; i <= 3; ++i) {
        if (b[i] == 1) {
            for (x = 99; x >= q[i]; --x) {
                recent[(x + 3)] = recent[x];
            }
            recent[(q[i])] = 'Y';
            recent[(q[i] + 1)] = 'o';
            recent[(q[i] + 2)] = 'u';
            recent[(q[i] + 3)] = ' ';
            recent[(q[i] + 4)] = 'a';
            recent[(q[i] + 5)] = 'r';
            recent[(q[i] + 6)] = 'e';
        }
    }
    
    printf("\n\nq[0] = %i\nq[1] = %i\nq[2] = %i\nq[3] = %i\n", q[0], q[1], q[2], q[3]);
    printf("\n\nb[0] = %i\nb[1] = %i\nb[2] = %i\nb[3] = %i\n", b[0], b[1], b[2], b[3]);
    
    /* Print final text */
    printf("\n%s\n", recent);
    
    /* System pauses */
    printf("\n");
    system("PAUSE");
    return 0;
}