Add 0560-wqsubarray-sum-equals-k.c

c/0560-subarray-sum-equals-k.c

@@ -0,0 +1,78 @@
+#define INIT_HASH_SIZE 4096
+
+// Represent an element in a hash table.
+typedef struct Hash {
+    int key;
+    int count;
+    struct Hash *next;
+} Hash;
+
+Hash *InitHash() {
+    Hash *h = (Hash*)calloc(INIT_HASH_SIZE, sizeof(Hash));
+    assert(h);
+    return h;
+}
+
+Hash *NewHash(int key) {
+    Hash *h = (Hash*)malloc(sizeof(Hash));
+    assert(h);
+    h->key = key;
+    h->count = 1;
+    h->next = NULL;
+    return h;
+}
+
+int HashKey(int key) {
+    while(key < 0) key += INIT_HASH_SIZE;
+    return (key % INIT_HASH_SIZE);
+}
+
+void AddHash(Hash *root, int key) {
+    assert(root);
+    Hash *h = &root[HashKey(key)];
+    if (h->key == 0 && h->count == 0) {
+        h->key = key;
+        h->count = 1;
+    } else if (h->key == key) {
+        h->count++;
+    } else {
+        while (h) {
+            if (h->key == key) {
+                h->count++;
+                return;
+            } else if (!h->next) {
+                h->next = NewHash(key);
+                return;
+            }
+            h = h->next;
+        }
+    }
+}
+
+// If hash not round return 0 on purpose.
+int GetHash(Hash *root, int key) {
+    Hash *h = &root[HashKey(key)];
+    while(h) {
+        if (h->key == key) {
+            return h->count;
+        }
+        h = h->next;
+    }
+    return 0;
+}
+
+int subarraySum(int* nums, int numsSize, int k){
+    Hash* hash = InitHash();
+    int sum = 0;
+    int res = 0;
+    int r = 0;
+
+    AddHash(hash, 0);
+    for(int i = 0; i < numsSize; i++){
+        sum += nums[i];
+        res += GetHash(hash, sum - k);
+        AddHash(hash, sum);
+    }
+
+    return res;
+}