// D. Scott
// CCI - Problem 3.1
// Implement 3 stacks using one array

public static void main (String[] args)
{
    // create array, set indices (st.1 at start, 3 at end, 2 at midpoint)
    int[] array = new int[75];
    int i1 = -1;
    int i3 = array.size();
    int i2 = array.size()/2;

    // Push 5 values onto stack 2
    System.out.println("Push 5 values onto stack 2:\n");
    for (int i = 1; i < 6; i++) {
        i2 = push2(array,i,i1,i2);
    }
    
    printArray(array,i1,i2,i3);
    
    // Push 11 values onto stack 3
    System.out.println("Push 11 values onto stack 3:\n");
    for (int i = 1; i < 12; i++) {    
        i3 = push3(array,i*2,i2,i3);
    }
    
    printArray(array,i1,i2,i3);


    // Push 22 value onto stack 1:
    System.out.println("Push 22 values onto stack 1:\n");
    for (int i = 1; i < 23; i++) {    
        i1 = push1(array,i+5,i1,i2);
    }
    printArray(array,i1,i2,i3);

    // Pop 1 value from stack 1:
    System.out.println("Pop a value from stack 1:\n");
    int value1 = pop1(array,i1,i2);
    if (value1 > 0){
        i1++;
        System.out.println("\tPopped value from stack 1: " + value1 + "\n");
    }
    printArray(array,i1,i2,i3);

    // Pop 4 values from stack 2:
    System.out.println("Pop 4 values from stack 2:\n")
    for (int i = 0; i < 4; i++) {
        int value2 = pop2(array,i2,i1);
        if (value2 > 0){
            i2++;
            System.out.println("\tPopped value from stack 2: " + value2 + "\n");
        }
    }
    printArray(array,i1,i2,i3);
    
    // Pop 7 values from stack 3:
    System.out.println("Pop 7 values from stack 3:\n")
    for (int i = 0; i < 7; i++) {
        int value3 = pop3(array,i3,i2);
        if (value3 > 0){
            i3++;
            System.out.println("\tPopped value from stack 3: " + value3 + "\n");
        }
    }
    printArray(array,i1,i2,i3);
    
    // Push 3 values onto stack 3:
    System.out.println("Push 3 values onto stack 3 (123,45,256):\n")
    i3 = push3(array,123,i2,i3);
    i3 = push3(array,45,i2,i3);
    i3 = push3(array,256,i2,i3);
    printArray(array,i1,i2,i3);
    

    // Pop 1 value from stack 3:
    System.out.println("Pop 1 value from stack 3:\n")
    int value3 = pop3(array,i3,i2);
    if (value3 > 0){
        i3++;
        System.out.println("\tPopped value from stack 3: " + value3 + "\n");
    }
    printArray(array,i1,i2,i3);
    
}

// Display the array(stacks w/separators)
void printArray(int[] a, int i1, int i2, int i3) {
    for (int i = 0; i < a.size(); i++) {
        if (i == i2 || i == i3)
            System.out.print(" | ");
        System.out.print(a[i]+" ");
    }
    System.out.println("\n");
}


int pop1(int[] a, int i1, int i2) {
    if (i1 >= 0 && i1 < i2) {
        int res = a[i1];
        a[i1++] = 0;
        return res;
    } else {
        return -1;    
    }
}

int pop2(int[] a, int i2, int i1) {
    if (i2 < a.size()/2) {
        int res = a[i2];
        a[i2++] = 0;
        return res;
    } else {
        return -1;
    }
}

int pop3(int[] a, int i3, int i2) {
    if (i3 > i2) {
        int res = a[i3];
        a[i3++] = 0;
        return res;
    } else {
        return -1;
    }
}

int push1(int[] a, int v, int i1, int i2) {
    if (i1+1 < i2) {
        a[++i1] = v;
        return i1;
    } else {
        System.out.println("Stack 1 is full.  Pop something first.");
        return i1;
    }
}

int push3(int[] a, int v, int i2, int i3) {
    if (i3-1 > a.size()/2) {
        a[--i3] = v;
        return i3;
    } else {
        System.out.println("Stack 3 is full.  Pop something first.");
        return i3;
    }
}

int push2(int[] a, int v, int i1, int i2) {
    if (i2-1 > i1) {
        a[--i2] = v;
        return i2;
    } else {
        System.out.println("Stack 2 is full.  Pop something first.");
        return i2;
    }
}