From 8833b7a5b246cad02e253838c07ba1689834e523 Mon Sep 17 00:00:00 2001
From: Ian C <ianc@noddybox.co.uk>
Date: Thu, 9 Dec 2021 13:32:48 +0000
Subject: Initial checkin

---
 3a.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 3a.c

(limited to '3a.c')

diff --git a/3a.c b/3a.c
new file mode 100644
index 0000000..e0b98e4
--- /dev/null
+++ b/3a.c
@@ -0,0 +1,182 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+static int FromBin(const char *p)
+{
+    size_t b = strlen(p) - 1;
+    int v = 0;
+    int f;
+
+    for(f = 0; p[f]; f++, b--)
+    {
+        if (p[f] == '1')
+        {
+            v |= 1 << b;
+        }
+    }
+
+    return v;
+}
+
+static void Chomp(char *p)
+{
+    size_t l = strlen(p);
+
+    while(l && p[l-1] == '\n')
+    {
+        p[--l] = 0;
+    }
+}
+
+int main(void)
+{
+    char nums[1000][14] = {0};
+    char work[1000][14] = {0};
+    char buff[80];
+    int bit[12] = {0};
+    int count = 0;
+    char str[13] = {0};
+    int b;
+    int f;
+    int n;
+    int oxygen;
+    int co2;
+    int lines = 0;
+
+    count = 0;
+
+    while(fgets(buff, sizeof buff, stdin))
+    {
+        Chomp(buff);
+        strcpy(nums[count++], buff);
+    }
+
+    lines = count;
+
+    count = 0;
+    memcpy(work, nums, sizeof nums);
+    b = 0;
+
+    while(count != 1)
+    {
+        for(f = 0; f < 12; f++)
+        {
+            bit[f] = 0;
+        }
+
+        count = 0;
+
+        for(n = 0; n < lines; n++)
+        {
+            if (work[n][0])
+            {
+                for(f = 0; f < 12; f++)
+                {
+                    if (work[n][f] == '1')
+                    {
+                        bit[f]++;
+                    }
+                }
+
+                count++;
+            }
+        }
+
+        if (count == 1)
+        {
+            for(n = 0; n < lines; n++)
+            {
+                if (work[n][0])
+                {
+                    oxygen = FromBin(work[n]);
+                }
+            }
+        }
+        else
+        {
+            char c;
+
+            c = bit[b] >= count/2.0 ? '1':'0';
+
+            for(n = 0; n < lines; n++)
+            {
+                if (work[n][b] != c)
+                {
+                    work[n][0] = 0;
+                }
+            }
+
+            if (b < 11)
+            {
+                b++;
+            }
+        }
+    }
+
+    count = 0;
+    memcpy(work, nums, sizeof nums);
+    b = 0;
+
+    while(count != 1)
+    {
+        for(f = 0; f < 12; f++)
+        {
+            bit[f] = 0;
+        }
+
+        count = 0;
+
+        for(n = 0; n < lines; n++)
+        {
+            if (work[n][0])
+            {
+                for(f = 0; f < 12; f++)
+                {
+                    if (work[n][f] == '1')
+                    {
+                        bit[f]++;
+                    }
+                }
+
+                count++;
+            }
+        }
+
+        if (count == 1)
+        {
+            for(n = 0; n < lines; n++)
+            {
+                if (work[n][0])
+                {
+                    co2 = FromBin(work[n]);
+                }
+            }
+        }
+        else
+        {
+            char c;
+
+            c = (bit[b] < count/2.0) ? '1':'0';
+
+            for(n = 0; n < lines; n++)
+            {
+                if (work[n][b] != c)
+                {
+                    work[n][0] = 0;
+                }
+            }
+
+            if (b < 11)
+            {
+                b++;
+            }
+        }
+    }
+
+    printf("oxygen %d\n", oxygen);
+    printf("co2 %d\n", co2);
+    printf("product %d\n", oxygen * co2);
+
+    return 0;
+}
-- 
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