Juan Céspedes - Computing 

Solved problems from UVa Online Judge 

Flooded!

815.c

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DIM 35
int matrix[DIM * DIM];
int m,n;
int flooded_regions;
int level;

static void
msort_merge(void *base, size_t nmemb1, size_t nmemb2, size_t size,
		int(*compar)(const void *, const void *)) {
	void * copy;
	int i,j;

	copy = malloc((nmemb1 + nmemb2) * size);
	if (!copy) {
		abort(); /* should exit with error code... */
	}
	memcpy(copy, base, (nmemb1 + nmemb2) * size);
	i = j = 0;
	for (i = j = 0; i+j < nmemb1+nmemb2; ) {
		if (j==nmemb2 ||
				(i!=nmemb1 &&
				 compar((char*)copy + i*size,(char*)copy + (nmemb1+j)*size)<0)) {
			memcpy((char*)base + (i+j)*size, (char*)copy + i*size, size);
			i++;
		} else {
			memcpy((char*)base + (i+j)*size, (char*)copy + (nmemb1+j)*size, size);
			j++;
		}
	}
}

void
msort(void *base, size_t nmemb, size_t size,
		int(*compar)(const void *, const void *)) {
	if (nmemb==1) {
		return;
	}

	/* sort 2 parts */
	msort(base, nmemb/2, size, compar);
	msort(((char *)(base) + (nmemb/2 * size)), nmemb - nmemb/2, size, compar);
	/* merge them */
	msort_merge(base, nmemb/2, nmemb - nmemb/2, size, compar);
}

static int
compar_int(const void *a, const void *b) {
	return *(int *)a - *(int *)b;
}

double
calculate(void) {
	int i;
	int curlevel = level;

	if (level <= 0) {
		flooded_regions = 0;
		return 0.0;
	}
	for (i=0; i<m*n-1; i++) {
		if (100 * (i+1) * (matrix[i+1] - matrix[i]) >= curlevel) {
			break;
		}
		curlevel -= 100 * (i+1) * (matrix[i+1] - matrix[i]);
	}
	flooded_regions = i+1;
	return (double)(matrix[i]) + (double)curlevel / (double)(100 * (i+1));
}

int
main(void) {
	int region=1;
	int i,j;

	while (1) {
		scanf("%d %d", &m, &n);
		if (m==0 && n==0) {
			break;
		}
		for (i=0; i<m; i++) {
			for (j=0; j<n; j++) {
				scanf("%d", &matrix[i * n + j]);
			}
		}
		scanf("%d", &level);

		msort(matrix, m*n, sizeof(int), compar_int);

		printf("Region %d\n", region++);
		printf("Water level is %.2f meters.\n", calculate());
		printf("%.2f percent of the region is under water.\n",
				100.0 * (double)flooded_regions / (m*n));
		printf("\n");
	}
	return 0;
}