Added generic hashmaps and 2 examples using them

examples/hm_basic.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#define LAZY_IMPL
+#include "../lazy.h"
+
+void printHmIdx(void *hm, int k) {
+  typedef Lz_HM(int,int) HM;
+  HM map = *(HM*)hm;
+  if (lz_hm_exists(map,k)) {
+    printf("hm[%d] = %d\n", k, lz_hm_get(map,k));
+  } else {
+    printf("hm[%d] = <N/A>\n", k);
+  }
+}
+
+int main() {
+  Lz_HM(int, int) hm;
+  lz_hm_init(hm);
+
+  lz_hm_add(hm, 1, 2);
+  lz_hm_add(hm, 2, 4);
+
+  printf("Hello World!\n");
+  printHmIdx(&hm, 1);
+  printHmIdx(&hm, 3);
+}

examples/hm_findsumpair.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#define LAZY_IMPL
+#include "../lazy.h"
+
+// This is some CS problem I heard of
+// You need to find any two indecies in the array which add to k
+// Hashmaps are the main way to solve this better than O(n^2)
+int main() {
+  int vals[] = {7, 12, 25, 30, 43, 60, 1000, 50, 38, 62, 50};
+  int N = sizeof(vals)/sizeof(vals[0]);
+  int K = 100;
+
+  Lz_HM(int,size_t) LUT;
+  lz_hm_init(LUT);
+
+  for (size_t i = 0; i < N; ++i) {
+    lz_hm_add(LUT, vals[i], i);
+  }
+
+  for (size_t i = 0; i < N; ++i) {
+    int v = vals[i];
+    int other = K-v;
+    if (lz_hm_exists(LUT, other)) {
+      size_t otherIdx = lz_hm_get(LUT, other);
+      if (otherIdx == i) continue;
+      printf("Found pair: idx: %zu, %zu, vals %d, %d\n",
+             i, otherIdx,
+             v, other);
+      break;
+    }
+  }
+  return 0;
+}