20251119 baekjoon

code_study/Baekjoon/c/1644.c

@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+int main() {
+    int N;
+    scanf("%d",&N);
+
+    bool* isPrime = (bool*)malloc(sizeof(bool)*(N+1));
+
+    for(int i=0; i<=N; i++) isPrime[i] = (i==0 || i==1) ? false : true;
+
+    for(int i=2; i*i<=N; i++) {
+        if(isPrime[i]) {
+            for(int j=i*i; j<=N; j+=i) {
+                isPrime[j] = false;
+            }
+        }
+    }
+
+    int prime_count = 0;
+    for(int i=0; i<=N; i++) if(isPrime[i]) prime_count++;
+    int* primes = (int*)malloc(sizeof(int)*(prime_count));
+    int idx=0;
+    for(int i=2; i<=N; i++) if(isPrime[i]) primes[idx++] = i;
+
+    int start = 0, end = 0;
+    int current_sum = 0;
+    int result = 0;
+
+    while(start < prime_count) {
+        while(end < prime_count && current_sum < N) current_sum += primes[end++];
+
+        if(current_sum == N) result++;
+
+        current_sum -= primes[start++];
+    }
+
+    printf("%d\n",result);
+
+    free(isPrime);
+    free(primes);
+
+    return 0;
+}