Ruqi

2DP.c

@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+//#include <math.h>
+
+void cumulative_sum(int *lst, int n, int *csum) {
+    csum[0] = 0;
+    for (int i = 1; i <= n; i++) {
+        csum[i] = csum[i - 1] + lst[i - 1];
+    }
+}
+
+void calculate_sump_matrix(int *lst, int n, int **result) {
+    int *csum = (int *)malloc((n + 1) * sizeof(int));
+    cumulative_sum(lst, n, csum);
+
+    for (int i = 0; i < n; i++) {
+        for (int j = i; j < n; j++) {
+            result[i][j] = csum[j + 1] - csum[i];
+        }
+    }
+
+    free(csum);
+}
+
+int DP(int n, int *list_p) {
+    int **R = (int **)malloc(n * sizeof(int *));
+    for (int i = 0; i < n; i++) {
+        R[i] = (int *)calloc(n, sizeof(int));
+    }
+
+    for (int i = 0; i < n - 1; i++) {
+        R[i][i + 1] = list_p[i] < list_p[i + 1] ? list_p[i] : list_p[i + 1];
+    }
+
+    int **sump_matrix = (int **)malloc(n * sizeof(int *));
+    for (int i = 0; i < n; i++) {
+        sump_matrix[i] = (int *)malloc(n * sizeof(int));
+    }
+
+    calculate_sump_matrix(list_p, n, sump_matrix);
+
+    for (int offset = 2; offset < n; offset++) {
+        for (int i = 0; i < n - offset; i++) {
+            int j = i + offset;
+            int left_k = i;
+            int right_k = j - 1;
+
+            while (left_k < right_k - 1) {
+                int mid_k = (left_k + right_k) / 2;
+                int left_value = sump_matrix[i][mid_k] + R[i][mid_k];
+                int right_value = sump_matrix[mid_k + 1][j] + R[mid_k + 1][j];
+
+                if (left_value > right_value) {
+                    right_k = mid_k;
+                } else {
+                    left_k = mid_k;
+                }
+            }
+
+            int tmp1 = sump_matrix[left_k + 1][j] + R[left_k + 1][j];
+            if (sump_matrix[i][left_k] + R[i][left_k] < tmp1) {
+                tmp1 = sump_matrix[i][left_k] + R[i][left_k];
+            }
+
+            int tmp2 = sump_matrix[right_k + 1][j] + R[right_k + 1][j];
+            if (sump_matrix[i][right_k] + R[i][right_k] < tmp2) {
+                tmp2 = sump_matrix[i][right_k] + R[i][right_k];
+            }
+
+            R[i][j] = tmp1 > tmp2 ? tmp1 : tmp2;
+        }
+    }
+
+    int result = R[0][n - 1];
+
+    for (int i = 0; i < n; i++) {
+        free(R[i]);
+        free(sump_matrix[i]);
+    }
+    free(R);
+    free(sump_matrix);
+
+    return result;
+}
+
+int main() {
+    int n;
+    scanf("%d", &n);
+
+    int *list_p = (int *)malloc(n * sizeof(int));
+    for (int i = 0; i < n; i++) {
+        scanf("%d", &list_p[i]);
+    }
+
+    printf("%d\n", DP(n, list_p));
+
+    free(list_p);
+    return 0;
+}

README.md

@@ -1,2 +1,4 @@
 # GithubDemo
 Learning how to use github for teams
+
+Nov 22, 2024