Add C solution

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diff --git a/challenge-181/paulo-custodio/c/ch-2.c b/challenge-181/paulo-custodio/c/ch-2.c
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+/*
+Challenge 181
+
+Task 2: Hot Day
+Submitted by: Mohammad S Anwar
+
+You are given file with daily temperature record in random order.
+
+Write a script to find out days hotter than previous day.
+Example
+
+Input File: (temperature.txt)
+
+2022-08-01, 20
+2022-08-09, 10
+2022-08-03, 19
+2022-08-06, 24
+2022-08-05, 22
+2022-08-10, 28
+2022-08-07, 20
+2022-08-04, 18
+2022-08-08, 21
+2022-08-02, 25
+
+Output:
+2022-08-02
+2022-08-05
+2022-08-06
+2022-08-08
+2022-08-10
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+struct data {
+    long jd;        // julian day
+    int temp;       // temperature
+};
+
+struct data* data = NULL;
+int data_size = 0;
+
+void* check_mem(void* p) {
+    if (!p) {
+        fputs("Out of memory", stderr);
+        exit(EXIT_FAILURE);
+    }
+    return p;
+}
+
+// https://pdc.ro.nu/jd-code.html
+long gregorian_date_to_jd(int y, int m, int d) {
+    y += 8000;
+    if (m < 3) { y--; m += 12; }
+    return (y * 365) + (y / 4) - (y / 100) + (y / 400) - 1200820
+        + (m * 153 + 3) / 5 - 92 + d - 1;
+}
+
+void jd_to_gregorian_date(long jd, int* yp, int* mp, int* dp) {
+    int y, m, d;
+    for (y = jd / 366 - 4715; gregorian_date_to_jd(y + 1, 1, 1) <= jd; y++);
+    for (m = 1; gregorian_date_to_jd(y, m + 1, 1) <= jd; m++);
+    for (d = 1; gregorian_date_to_jd(y, m, d + 1) <= jd; d++);
+    *yp = y; *mp = m; *dp = d;
+}
+
+void read_data(const char* filename) {
+    FILE* fp = fopen(filename, "r");
+    if (fp == NULL) {
+        perror(filename);
+        exit(EXIT_FAILURE);
+    }
+
+    char line[BUFSIZ];
+    while (fgets(line, sizeof(line), fp)) {
+        int y,m,d,t;
+        if (sscanf(line, "%d-%d-%d, %d", &y, &m, &d, &t) != 4) {
+            fprintf(stderr, "cannot parse: %s\n", line);
+            exit(EXIT_FAILURE);
+        }
+        struct data d1;
+        d1.jd = gregorian_date_to_jd(y, m, d);
+        d1.temp = t;
+
+        data_size++;
+        data = check_mem(realloc(data, data_size*sizeof(struct data)));
+        data[data_size-1] = d1;
+    }
+
+    fclose(fp);
+}
+
+int compare(const void* a, const void* b) {
+    return ((struct data*)a)->jd - ((struct data*)b)->jd;
+}
+
+void print_hot_days() {
+    qsort(data, data_size, sizeof(struct data), compare);
+    for (int i = 1; i < data_size; i++) {
+        if (data[i].temp > data[i-1].temp) {
+            int y, m, d;
+            jd_to_gregorian_date(data[i].jd, &y, &m, &d);
+            printf("%04d-%02d-%02d\n", y, m, d);
+        }
+    }
+}
+
+int main(int argc, char* argv[]) {
+    if (argc != 2) {
+        fputs("usage: ch-2 temperature-file\n", stderr);
+        return EXIT_FAILURE;
+    }
+
+    read_data(argv[1]);
+    print_hot_days();
+    free(data);
+}