90！

2023208/main.cpp

@@ -4,7 +4,7 @@
 
 double A[5051] = {0};
 double point_xs[101] = {0};
-long double t[101] = {0};
+int valid_point_num = 0;
 
 double get_num(int row, int col) {
     if (col > row) {
@@ -25,23 +25,31 @@ bool compare_double(long double a, long double b) {
 }
 
 double evaluate(double x, int highest) {
-    double ans = t[highest];
+    double ans = get_num(highest, highest);
     for (int j = highest - 1; j >= 0; j--) {
         ans *= x - point_xs[j];
-        ans += t[j];
+        ans += get_num(j, j);
     }
     return ans;
 }
 
+int display_mat() {
+    for (int i = 0; i < valid_point_num; i++) {
+        for (int j = 0; j < valid_point_num; j++) {
+            printf("%lf ", get_num(i, j));
+        }
+        printf("\n");
+    }
+    printf("\n");
+    return 0;
+}
+
 int main() {
-    int n = 0, m = 0;
-    int valid_point_num = 0;
-    // freopen("lambdaeight9.in", "r", stdin);
-    scanf("%d", &n);
-    scanf("%d", &m);
-    double read_x, read_y;
-    bool found_duplicate = false;
+    int n, m;
+    scanf("%d %d", &n, &m);
     for (int i = 0; i < n; i++) {
+        bool found_duplicate = false;
+        double read_x, read_y;
         scanf("%lf %lf", &read_x, &read_y);
         for (int j = 0; j < valid_point_num; j++) {
             if (compare_double(read_x, point_xs[j])) {
@@ -52,47 +60,41 @@ int main() {
 
         if (!found_duplicate) {
             point_xs[valid_point_num] = read_x;
-            t[valid_point_num] = read_y;
+            set_num(valid_point_num, 0, read_y);
             valid_point_num++;
         }
     }
 
-    // Prepare the matrix
-    for (int row = 0; row < valid_point_num; row++) {
-        set_num(row, 0, 1);
-        for (int col = 1; col <= row; col++) {
-            set_num(row, col, get_num(row, col - 1) * (point_xs[row] - point_xs[col - 1]));
+    // Go create the full table
+    for (int col = 1; col < valid_point_num; col++) {
+        int delta = col;
+        for (int row = col; row < valid_point_num; row++) {
+            set_num(row, col, (get_num(row, col - 1) - get_num(row - 1, col - 1)) / (point_xs[row] - point_xs[row - delta]));
         }
+        if (compare_double(get_num(col, col) / 1000, 0)) {
+            set_num(col, col, 0);
+        }
+        // display_mat();
     }
 
-    // Solve for t
-    for (int row = 0; row < valid_point_num; row++) {
-        for (int i = 0; i < row; i++) {
-            t[row] -= t[i] * get_num(row, i);
-        }
-        if (compare_double(t[row] / 1000, 0)) {
-            t[row] = 0;
-        } 
-        else {
-            t[row] /= get_num(row, row);
-        }
-    }
 
-    // Find for highest exponent
+    // Find the highest
     int highest = valid_point_num - 1;
     for (; highest >= 0; highest--) {
-        if (!compare_double(t[highest], 0)) {
-            break;
+        if (compare_double(get_num(highest, highest) / 1000, 0)) {
+            continue;
         }
+        break;
     }
 
     printf("%d\n", highest);
 
-    // Evaluate
+    double to_be_evaled = 0;
     for (int i = 0; i < m; i++) {
-        double to_be_evaled = 0; 
         scanf("%lf", &to_be_evaled);
         printf("%lf\n", evaluate(to_be_evaled, highest));
     }
+
+    
     return 0;
 }