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// 900. RLE Iterator
#include "leetcode.h"
/*
* we can use run length encoding to encode a sequence of integers. in a run
* length encoded array of even length encoding, for all even 'i', 'encoding[i]'
* tells us the number of times that the non negative integer value 'encoding[i
* + 1]' is repeated in the sequence. given that a run length encoded array,
* design an iterator that iterates through it.
*/
typedef struct {
int *val;
int *cnt;
int size;
int curr;
} RLEIterator;
RLEIterator *rLEIteratorCreate(int *encoding, int encodingSize) {
int size = encodingSize / 2, idx = 0;
int *val = (int *)malloc(size * sizeof(int));
int *cnt = (int *)malloc(size * sizeof(int));
for (int i = 0; i < size; i++) {
if (!encoding[2 * i])
continue;
val[idx] = encoding[2 * i + 1];
cnt[idx] = encoding[2 * i];
idx++;
}
val = realloc(val, idx * sizeof(int));
cnt = realloc(cnt, idx * sizeof(int));
RLEIterator *res = malloc(sizeof(RLEIterator));
res->val = val;
res->cnt = cnt;
res->size = idx;
res->curr = 0;
return res;
}
int rLEIteratorNext(RLEIterator *obj, int n) {
if (obj->curr >= obj->size)
return -1;
int res = -1, items = n, p = obj->curr, *cnt = obj->cnt;
while (items && p < obj->size) {
if (cnt[p] > items) {
cnt[p] -= items;
items = 0;
res = obj->val[p];
} else {
items -= cnt[p];
if (!items)
res = obj->val[p];
cnt[p] = 0;
p++;
}
}
obj->curr = p;
return res;
}
void rLEIteratorFree(RLEIterator *obj) {
free(obj->val);
free(obj->cnt);
free(obj);
}
int main() {
int e1[] = {3, 8, 0, 9, 2, 5};
RLEIterator *obj = rLEIteratorCreate(e1, ARRAY_SIZE(e1));
printf("%d\n", rLEIteratorNext(obj, 2)); // expect: 8
printf("%d\n", rLEIteratorNext(obj, 1)); // expect: 8
printf("%d\n", rLEIteratorNext(obj, 1)); // expect: 5
printf("%d\n", rLEIteratorNext(obj, 2)); // expect: -1
}
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