Added solutions for 15, 16, 17, 18 and 19

2 files changed, 147 insertions, 0 deletions

diff --git a/2023/17/17a.c b/2023/17/17a.c
new file mode 100644
index 0000000..0b02f45
--- /dev/null
+++ b/2023/17/17a.c
@@ -0,0 +1,73 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define M 150
+#define MAXE 1000000
+#define INF 999999999
+
+#define E 0
+#define N 1
+#define W 2
+#define S 3
+
+int go[4][2] = { [E] = {0, 1}, [N] = {-1, 0}, [W] = {0, -1}, [S] = {1, 0} };
+
+typedef struct { int i, j, k, s, d; } node_t;
+
+char map[M][M];
+int n, nq, d[M][M][4][4];
+node_t heap[MAXE];
+
+void swap(int i, int j) {
+        node_t aux = heap[i];
+        heap[i] = heap[j];
+        heap[j] = aux;
+}
+
+void push(node_t node) {
+        heap[nq] = node;
+        for (int k = nq++; k > 0 && heap[k].d < heap[(k-1)/2].d; k = (k-1)/2)
+                swap(k, (k-1)/2);
+}
+
+node_t pop(void) {
+        node_t ret = heap[0];
+        heap[0] = heap[--nq];
+        for (int k = 0, j = 0; 2*k+1 < nq; k = j) {
+                j = 2*k+1;
+                if (j+1 < nq && heap[j].d > heap[j+1].d) j++;
+                if (heap[k].d > heap[j].d) swap(k, j);
+        }
+        return ret;
+}
+
+int main() {
+        for (n = 0; fgets(map[n], M, stdin) != NULL; n++) ;
+
+        for (int i = 0; i < n; i++)
+                for (int j = 0; j < n; j++)
+                        for (int k = 0; k < 4; k++)
+                                for (int s = 0; s < 4; s++)
+                                        d[i][j][k][s] = INF;
+
+        push((node_t){.i = 0, .j = 0, .k = -1, .s = 0});
+        node_t v;
+        for (v = pop(); v.i != n-1 || v.j != n-1; v = pop()) {
+                for (int k = 0; k < 4; k++) {
+                        if (k == v.k + 2 || k == v.k - 2) continue;
+                        int ii = v.i+go[k][0];
+                        int jj = v.j+go[k][1];
+                        if (ii < 0 || jj < 0 || ii >= n || jj >= n) continue;
+                        int ss = k == v.k ? v.s + 1 : 1;
+                        int dd = v.d + map[ii][jj] - '0';
+                        if (d[ii][jj][k][ss] <= dd || ss > 3) continue;
+                        d[ii][jj][k][ss] = dd;
+                        push((node_t){.i=ii, .j=jj, .k=k, .s=ss, .d=dd});
+                }
+        }
+
+        printf("%d\n", v.d);
+        return 0;
+}
diff --git a/2023/17/17b.c b/2023/17/17b.c
new file mode 100644
index 0000000..10fad81
--- /dev/null
+++ b/2023/17/17b.c
@@ -0,0 +1,74 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define M 150
+#define MAXE 1000000
+#define INF 999999999
+
+#define E 0
+#define N 1
+#define W 2
+#define S 3
+
+int go[4][2] = { [E] = {0, 1}, [N] = {-1, 0}, [W] = {0, -1}, [S] = {1, 0} };
+
+typedef struct { int i, j, k, s, d; } node_t;
+
+char map[M][M];
+int n, nq, d[M][M][4][11];
+node_t heap[MAXE];
+
+void swap(int i, int j) {
+        node_t aux = heap[i];
+        heap[i] = heap[j];
+        heap[j] = aux;
+}
+
+void push(node_t node) {
+        heap[nq] = node;
+        for (int k = nq++; k > 0 && heap[k].d < heap[(k-1)/2].d; k = (k-1)/2)
+                swap(k, (k-1)/2);
+}
+
+node_t pop(void) {
+        node_t ret = heap[0];
+        heap[0] = heap[--nq];
+        for (int k = 0, j = 0; 2*k+1 < nq; k = j) {
+                j = 2*k+1;
+                if (j+1 < nq && heap[j].d > heap[j+1].d) j++;
+                if (heap[k].d > heap[j].d) swap(k, j);
+        }
+        return ret;
+}
+
+int main() {
+        for (n = 0; fgets(map[n], M, stdin) != NULL; n++) ;
+
+        for (int i = 0; i < n; i++)
+                for (int j = 0; j < n; j++)
+                        for (int k = 0; k < 4; k++)
+                                for (int s = 0; s < 11; s++)
+                                        d[i][j][k][s] = INF;
+
+        push((node_t){.i = 0, .j = 0, .k = -1, .s = 0});
+        node_t v;
+        for (v = pop(); v.i != n-1 || v.j != n-1; v = pop()) {
+                for (int k = 0; k < 4; k++) {
+                        if (k == v.k + 2 || k == v.k - 2) continue;
+                        if (v.s < 4 && v.k != -1 && v.k != k) continue;
+                        int ii = v.i+go[k][0];
+                        int jj = v.j+go[k][1];
+                        if (ii < 0 || jj < 0 || ii >= n || jj >= n) continue;
+                        int ss = k == v.k ? v.s + 1 : 1;
+                        int dd = v.d + map[ii][jj] - '0';
+                        if (d[ii][jj][k][ss] <= dd || ss > 10) continue;
+                        d[ii][jj][k][ss] = dd;
+                        push((node_t){.i=ii, .j=jj, .k=k, .s=ss, .d=dd});
+                }
+        }
+
+        printf("%d\n", v.d);
+        return 0;
+}