demo

bangoc · Jan 14, 2024 · 01550da · 01550da
1 parent c6cb65f
commit 01550da
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Showing 6 changed files with 1,116 additions and 22 deletions.
diff --git a/algo/algo.h b/algo/algo.h
@@ -47,21 +47,38 @@ static void q2sort(void *a, int n, int sz, compare_fnt cmp) {
   q2sort(right, (a - right)/sz + n, sz, cmp);
 }
 
-static int binsearch(const void *a, int n, int sz, const void *v, compare_fnt cmp) {
-  int l = 0, r = n - 1;
+static void *binsearch(const void *k, void *a, int n, int sz, compare_fnt cmp) {
+  int l = 0, r = n - 1, m, o;
   while (l <= r) {
-    int m = (l + r) / 2;
-    int x = cmp(a + m * sz, v);
-    if (x == 0) {
-      return m;
+    m = (l + r) / 2;
+    o = cmp(k, a + m * sz);
+    if (o == 0) {
+      return a + m * sz;
     }
-    if (x < 0) {
+    if (o < 0) {
+      r = m - 1;
+    } else {
       l = m + 1;
-    } else if (x > 0) {
+    }
+  }
+  return NULL;
+}
+
+static void *bnear_search(const void *k, void *a, int n, int sz, compare_fnt cmp) {
+  int l = 0, r = n - 1, m = 0, o;
+  while (l <= r) {
+    m = (l + r) / 2;
+    o = cmp(k, a + m * sz);
+    if (o == 0) {
+      break;
+    }
+    if (o < 0) {
       r = m - 1;
+    } else {
+      l = m + 1;
     }
   }
-  return -1;
+  return a + m * sz;
 }
 
 #define HTOP(i) (((i) - 1) >> 1)

diff --git a/all/cgen.h b/all/cgen.h
@@ -114,21 +114,37 @@ static void q2sort(void *a, int n, int sz, compare_fnt cmp) {
   q2sort(a, (left - a)/sz + 1, sz, cmp);
   q2sort(right, (a - right)/sz + n, sz, cmp);
 }
-static int binsearch(const void *a, int n, int sz, const void *v, compare_fnt cmp) {
-  int l = 0, r = n - 1;
+static void *binsearch(const void *k, void *a, int n, int sz, compare_fnt cmp) {
+  int l = 0, r = n - 1, m, o;
   while (l <= r) {
-    int m = (l + r) / 2;
-    int x = cmp(a + m * sz, v);
-    if (x == 0) {
-      return m;
+    m = (l + r) / 2;
+    o = cmp(k, a + m * sz);
+    if (o == 0) {
+      return a + m * sz;
     }
-    if (x < 0) {
+    if (o < 0) {
+      r = m - 1;
+    } else {
       l = m + 1;
-    } else if (x > 0) {
+    }
+  }
+  return NULL;
+}
+static void *bnear_search(const void *k, void *a, int n, int sz, compare_fnt cmp) {
+  int l = 0, r = n - 1, m = 0, o;
+  while (l <= r) {
+    m = (l + r) / 2;
+    o = cmp(k, a + m * sz);
+    if (o == 0) {
+      break;
+    }
+    if (o < 0) {
       r = m - 1;
+    } else {
+      l = m + 1;
     }
   }
-  return -1;
+  return a + m * sz;
 }
 #define HTOP(i) (((i) - 1) >> 1)
 #define HLEFT(i) (((i) << 1) + 1)

diff --git a/tests/cgen/CMakeLists.txt b/tests/cgen/CMakeLists.txt
@@ -10,4 +10,6 @@ add_executable(max_heap_int_demo max_heap_int_demo.c)
 add_executable(perm_demo perm_demo.c)
 add_executable(comb_demo comb_demo.c)
 add_executable(map_of_vector map_of_vector.c)
-add_executable(tmap_kv_demo tmap_kv_demo.c)
+add_executable(tmap_kv_demo tmap_kv_demo.c)
+add_executable(bnear_search_demo bnear_search_demo.c)
+add_executable(topk_demo topk_demo.c)
diff --git a/tests/cgen/bnear_search_demo.c b/tests/cgen/bnear_search_demo.c
@@ -0,0 +1,24 @@
+#include "cgen.h"
+#include <stdio.h>
+int icmp(const void *p1, const void *p2) {
+  return *(const int*)p1 - *(const int *)p2;
+}
+int main(int argc, char *argv[]) {
+  int a[] = {1, 3, 5, 7, 9, 11, 20, 22, 24, 26, 28, 30};
+  int n = sizeof(a)/sizeof(a[0]);
+  int k;
+  if (argc == 1) {
+    printf("Usage: binsearch xyz\n");
+    return 0;
+  }
+  for (int i = 1; i < argc; ++i) {
+    sscanf(argv[i], "%d", &k);
+    int *pos = bnear_search(&k, a, n, sizeof(int), icmp);
+    if (*pos == k) {
+      printf("Found %d at position %ld\n", k, pos - a);
+    } else {
+      printf("Not found %d.", k);
+      printf(" Near %ld - %d\n", pos - a, *pos);
+    }
+  }
+}
diff --git a/tests/cgen/bsearch_demo.c b/tests/cgen/bsearch_demo.c
@@ -6,13 +6,18 @@ int icmp(const void *p1, const void *p2) {
 int main(int argc, char *argv[]) {
   int a[] = {1, 3, 5, 7, 9, 11, 20, 22, 24, 26, 28, 30};
   int n = sizeof(a)/sizeof(a[0]);
-  int v;
+  int k;
   if (argc == 1) {
     printf("Usage: binsearch xyz\n");
     return 0;
   }
   for (int i = 1; i < argc; ++i) {
-    sscanf(argv[i], "%d", &v);
-    printf("%d\n", binsearch(a, n, sizeof(int), &v, icmp));
+    sscanf(argv[i], "%d", &k);
+    int *pos = binsearch(&k, a, n, sizeof(int), icmp);
+    if (pos) {
+      printf("Found %d at position %ld\n", k, pos - a);
+    } else {
+      printf("Not found %d\n", k);
+    }
   }
 }