From 61400d87e2e3fa5363eed7a9ad6cf160663438d5 Mon Sep 17 00:00:00 2001
From: laura <laura@ccc.ac>
Date: Mon, 8 Dec 2025 22:26:56 +0100
Subject: [PATCH] made 2-1 acceptably fast

---
 2/main.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 70 insertions(+), 13 deletions(-)

diff --git a/2/main.c b/2/main.c
index c1434c0..d45a6ef 100644
--- a/2/main.c
+++ b/2/main.c
@@ -18,6 +18,8 @@ char input[] =
 int width = 0;
 int height = 0;
 uint64_t result = 0;
+uint64_t result_2 = 0;
+
 
 uint64_t parseNum(char* str, int* len){
     int i = 0;
@@ -81,11 +83,60 @@ void sort_ranges(uint64_t* starts, uint64_t* ends, int len){
     }
 }
 
+//splits ranges that go over a decimal overflow barrier into two (or if necessary more) ranges
+void optimize_ranges(uint64_t* starts, uint64_t* ends, int* len){
+    for(int i = 0; i<(*len); i++){
+        if(numPlaces(starts[i])<numPlaces(ends[i])){
+            //printf("Range %lu - %lu crosses barrier\n", starts[i], ends[i]);
+            ends[*len] = ends[i];
+            ends[i] = power(10, numPlaces(starts[i]))-1;
+            starts[*len] = power(10, numPlaces(starts[i]));
+            (*len)++;
+            
+
+            //printf("Split into %lu - %lu\n", starts[i], ends[i]);
+            //printf("and %lu - %lu\n\n", starts[*len], ends[*len]);
+        }
+    }
+
+}
+
+uint64_t sumup(uint64_t a, uint64_t b){
+    uint64_t res = 0;
+    for(uint64_t i = a; i<=b; i++){
+        res += i;
+    }
+    return res;
+}
+
+uint64_t sum_gauss(uint64_t a){
+    return (a*(a+1))/2;
+}
+
+uint64_t sumup_gauss(uint64_t a, uint64_t b){
+    return sum_gauss(b)-sum_gauss(a-1);
+}
+
+uint64_t check_range(uint64_t start, uint64_t end){
+    int num = numPlaces(start);
+    if(!(num%2)){
+        uint64_t div = 1+power(10, num/2);
+        uint64_t a = ((start+div-1)/div);
+        uint64_t b = (end)/div;
+        //uint64_t sum = sumup(a, b);
+        uint64_t sum = sumup_gauss(a, b);
+        //printf("Range %lu - %lu\nsumup: \t%lu\nsumup_gauss: \t%lu\n\n", start, end, sum, sum2);
+
+        return sum*div;
+    }
+    return 0;
+}
+
 int main(int argc, char *argv[]){
     clock_t start, end;
     start = clock();
 
-    printf("INT_MAX: %d\n", INT_MAX);
+    //printf("INT_MAX: %d\n", INT_MAX);
 
     int i = 0;
     int num_ranges = 1;
@@ -96,8 +147,8 @@ int main(int argc, char *argv[]){
         i++;
     }
 
-    uint64_t starts[num_ranges];
-    uint64_t ends[num_ranges];
+    uint64_t starts[num_ranges*2];
+    uint64_t ends[num_ranges*2];
 
     i = 0;
     int range_num = 0;
@@ -112,18 +163,23 @@ int main(int argc, char *argv[]){
         range_num++;
     }
 
-    sort_ranges(starts, ends, num_ranges);
+
+
+    optimize_ranges(starts, ends, &num_ranges);
 
     for(i = 0; i<num_ranges; i++){
-        printf("checking range %lu-%lu\n\n", starts[i], ends[i]);
-        for(uint64_t o = starts[i]; o<=ends[i]; o++){
-            //printf("checking %d for sillyness\n", o);
-            if(check_silly(o)){
-                result += o;
-                printf("%lu is SILLY!\t\tcount is %lu\n", o, result);
-                
-            }
-        }
+        //printf("checking range %lu-%lu\n", starts[i], ends[i]);
+        result_2 += check_range(starts[i], ends[i]);
+        //for(uint64_t o = starts[i]; o<=ends[i]; o++){
+        //    //printf("checking %d for sillyness\n", o);
+        //    if(check_silly(o)){
+        //        result += o;
+        //        //printf("%lu is SILLY!\t\tcount is %lu\n", o, result);
+        //        
+        //    }
+        //}
+        //printf("count: %lu\n", result);
+        //printf("count_2: %lu\n\n", result_2);
     }
     
     //if(check_silly(1212)){
@@ -134,6 +190,7 @@ int main(int argc, char *argv[]){
 
     end = clock();
     printf("count: %lu\n", result);
+    printf("count_2: %lu\n", result_2);
     clock_t ticks_taken = end - start; 
     double time_taken = ((double)ticks_taken)/CLOCKS_PER_SEC;
     printf("time take: %f ticks\n", time_taken);