add day5

day5/findvalid.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+    "fmt"
+    "os"
+    "strings"
+    "strconv"
+)
+
+func check(e error) {
+    if e != nil { panic(e) }
+}
+
+func contains(slice []int, element int) bool {
+    for _, value := range slice {
+        if value == element {
+            return true
+        }
+    }
+    return false
+}
+
+func get_prerequisites(rules [][2]int, target int) []int {
+    out := make([]int, 0, 10)
+
+    // find rules
+    for _, rule := range rules {
+        if rule[1] == target && !contains(out, rule[0]) {
+            out = append(out, rule[0])
+        }
+    }
+
+    return out
+}
+
+func main() {
+
+    dat, err := os.ReadFile("data.txt")
+    check(err)
+    dat_str := string(dat[:len(dat) - 1])
+
+
+    blocks := strings.Split(dat_str, "\n\n")
+
+    rules := make([][2]int, 0, 1000)
+    for _, rule := range strings.Split(blocks[0], "\n") {
+        str_rules := strings.Split(rule, "|")
+
+        num1, err := strconv.Atoi(str_rules[0])
+        check(err)
+        num2, err := strconv.Atoi(str_rules[1])
+        check(err)
+
+        rules = append(rules, [2]int{ num1, num2 })
+    }
+
+    orderings := make([][]int, 0, 1000)
+    for _, line := range strings.Split(blocks[1], "\n") {
+        str_orderings := strings.Split(line, ",")
+
+        elements := make([]int, 0, len(str_orderings))
+        for _, elem := range str_orderings {
+            num, err := strconv.Atoi(elem)
+            check(err)
+
+            elements = append(elements, num)
+        }
+
+        orderings = append(orderings, elements)
+    }
+    
+    // check orderings
+    acc := 0
+    var pre []int
+    for _, ordering := range orderings {
+
+        // check single line
+        valid := true
+        for i := len(ordering) - 1; i >= 0; i-- {
+            pre = get_prerequisites(rules, ordering[i])
+            
+            for _, p := range pre {
+                if contains(ordering, p) {
+                    if !contains(ordering[:i], p) {
+                        valid = false 
+                        break
+                    }
+                }
+            }
+            if !valid { break }
+        }
+        
+        // add middle elem to acc
+        if valid {
+            acc += ordering[len(ordering)/2]
+        }
+    }
+
+    fmt.Println(acc)
+}