rain container

container.c

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#define max(A, B) ((A) > (B) ? (A) : (B))
#define min(A, B) ((A) < (B) ? (A) : (B))

int contained(int *cont, size_t len) {
    if (len == 0) {
        return 0;
    }

    int *left = (int *) malloc(sizeof(int) * len);
    assert(left);
    left[0] = cont[0];
    for (int i=1; i<len; ++i) {
        left[i] = max(left[i-1], cont[i]);
    }

    int *right = (int *) malloc(sizeof(int) * len);
    assert(right);
    right[len-1] = cont[len-1];
    for (int i=len-2; i>=0; --i) {
        right[i] = max(right[i+1], cont[i]);
    }

    int sum = 0;
    for (int i=0; i<len; ++i) {
        int h = min(left[i], right[i]);
        if (h > cont[i]) {
            sum += h - cont[i];
        }
    }

    free(left);
    free(right);

    return sum;
}

int main(int argc, char *argv[]) {
    const int len = argc - 1;
    int *container = (int *) malloc(sizeof(int) * len);
    assert(container);
    for (int i=0; i<len; ++i) {
        container[i] = atoi(argv[i+1]);
    }
    printf("%d\n", contained(container, len));
    free(container);
    return 0;
}