1D & 2D Arrays
with Pointers in C

#include <stdio.h>

int main() {
    int temp[] = { 32, 35, 29, 41, 38, 27, 33 };
    int  n    = sizeof(temp) / sizeof(temp[0]);
    int *p    = temp;   /* p points to temp[0] */

    printf("=== Temperatures (7 days) ===\n\n");

    /* Method 1: arr[i] — classic index notation */
    printf("Method 1 — arr[i]          : ");
    for (int i = 0; i < n; i++) printf("%d ", temp[i]);
    printf("\n");

    /* Method 2: *(arr + i) — pointer arithmetic */
    printf("Method 2 — *(arr+i)        : ");
    for (int i = 0; i < n; i++) printf("%d ", *(temp + i));
    printf("\n");

    /* Method 3: p[i] — pointer used like an array */
    printf("Method 3 — p[i]            : ");
    for (int i = 0; i < n; i++) printf("%d ", p[i]);
    printf("\n");

    /* Method 4: *p++ — walk pointer forward */
    printf("Method 4 — *p++            : ");
    p = temp;   /* reset to start */
    for (int i = 0; i < n; i++) printf("%d ", *p++);
    printf("\n");

    /* Show addresses — each element is 4 bytes apart */
    printf("\n--- Addresses (each 4 bytes apart) ---\n");
    for (int i = 0; i < n; i++)
        printf("  temp[%d] = %2d  address = %p  (arr+%d = %p)\n",
               i, temp[i], (void*)&temp[i],
               i, (void*)(temp + i));

    printf("\narr == &arr[0] : %s\n",
           temp == &temp[0] ? "TRUE" : "FALSE");
    return 0;
}

#include <stdio.h>

void printArr(int *p, int n) {
    for (int i = 0; i < n; i++) printf("%d ", *p++);
    printf("\n");
}

/* Reverse array in-place using two pointers */
void reverseArr(int *arr, int n) {
    int *lo = arr;           /* left  pointer */
    int *hi = arr + n - 1;  /* right pointer */
    while (lo < hi) {
        int tmp = *lo;
        *lo++ = *hi;
        *hi-- = tmp;
    }
}

/* Linear search: return pointer to match, NULL if absent */
int* findVal(int *arr, int n, int target) {
    int *end = arr + n;
    for (int *p = arr; p < end; p++)
        if (*p == target) return p;
    return NULL;
}

/* Sum using only pointer walk, no index variable */
int sumArr(int *arr, int n) {
    int sum = 0;
    int *end = arr + n;
    for (int *p = arr; p < end; p++) sum += *p;
    return sum;
}

int main() {
    int scores[] = { 88, 42, 95, 67, 73, 55, 91 };
    int n = sizeof(scores) / sizeof(scores[0]);

    printf("Original : "); printArr(scores, n);

    /* Sum */
    printf("Sum      : %d\n", sumArr(scores, n));
    printf("Average  : %.2f\n\n", (double)sumArr(scores, n) / n);

    /* Search */
    int  target = 73;
    int *found  = findVal(scores, n, target);
    if (found)
        printf("Search %d : found at index %td  address %p\n\n",
               target, found - scores, (void*)found);
    else
        printf("Search %d : not found\n\n", target);

    /* Reverse */
    reverseArr(scores, n);
    printf("Reversed : "); printArr(scores, n);

    /* Pointer subtraction demo */
    int *first = scores;
    int *last  = scores + n - 1;
    printf("\nlast - first = %td elements apart\n", last - first);
    return 0;
}

#include <stdio.h>

/* READ-ONLY: const protects the array */
void printArr(const int *arr, int n) {
    printf("  [ ");
    for (int i = 0; i < n; i++) printf("%d ", arr[i]);
    printf("]\n");
}

/* MODIFYING: doubles every element in-place */
void doubleAll(int *arr, int n) {
    for (int i = 0; i < n; i++) arr[i] *= 2;
}

/* STATISTICS: multiple return values via output pointers */
void stats(const int *arr, int n,
           int *outMin, int *outMax, double *outAvg) {
    int sum = 0;
    *outMin = *outMax = arr[0];
    for (int i = 0; i < n; i++) {
        sum += arr[i];
        if (arr[i] < *outMin) *outMin = arr[i];
        if (arr[i] > *outMax) *outMax = arr[i];
    }
    *outAvg = (double)sum / n;
}

/* CLAMP: replaces out-of-range values in-place */
int clamp(int *arr, int n, int lo, int hi) {
    int changes = 0;
    for (int *p = arr, *end = arr + n; p < end; p++) {
        if      (*p < lo) { *p = lo; changes++; }
        else if (*p > hi) { *p = hi; changes++; }
    }
    return changes;
}

int main() {
    int marks[] = { 45, 112, 78, -5, 92, 63, 150, 55 };
    int n = sizeof(marks) / sizeof(marks[0]);

    printf("Original marks:\n"); printArr(marks, n);

    /* Stats before clamp */
    int mn, mx; double avg;
    stats(marks, n, &mn, &mx, &avg);
    printf("  Min=%d  Max=%d  Avg=%.2f\n\n", mn, mx, avg);

    /* Clamp to valid range [0..100] */
    int c = clamp(marks, n, 0, 100);
    printf("After clamp [0..100] — %d value(s) fixed:\n", c);
    printArr(marks, n);

    /* Stats after clamp */
    stats(marks, n, &mn, &mx, &avg);
    printf("  Min=%d  Max=%d  Avg=%.2f\n\n", mn, mx, avg);

    /* Double all marks (modifying) */
    doubleAll(marks, n);
    printf("After doubleAll (modified in-place):\n");
    printArr(marks, n);
    return 0;
}