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2023208/main.cpp

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+#include <stdio.h>
+#include <iostream>
+
+double A[5051] = {0};
+double point_xs[101] = {0};
+double t[101] = {0};
+
+double get_num(int row, int col) {
+    if (col > row) {
+        return 0;
+    }
+    return A[row * (row + 1) / 2 + col];
+}
+
+double set_num(int row, int col, double content) {
+    if (col > row) {
+        return 0;
+    }
+    return A[row * (row + 1) / 2 + col] = content;
+}
+
+bool compare_double(double a, double b) {
+    return (a - b > 0 ? a - b : -(a - b)) < 0.000001;
+}
+
+double evaluate(double x, int highest) {
+    double ans = t[highest];
+    for (int j = highest - 1; j >= 0; j--) {
+        ans *= x - point_xs[j];
+        ans += t[j];
+    }
+    return ans;
+}
+
+int main() {
+    int n = 0, m = 0;
+    int valid_point_num = 0;
+    scanf("%d", &n);
+    scanf("%d", &m);
+    double read_x, read_y;
+    bool found_duplicate = false;
+    for (int i = 0; i < n; i++) {
+        scanf("%lf %lf", &read_x, &read_y);
+        for (int j = 0; j < valid_point_num; j++) {
+            if (compare_double(read_x, point_xs[valid_point_num])) {
+                found_duplicate = true;
+                break;
+            }
+        }
+
+        if (!found_duplicate) {
+            point_xs[++valid_point_num] = read_x;
+            t[valid_point_num] = read_y;
+        }
+    }
+
+    // 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]));
+        }
+    }
+
+    // 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);
+        }
+        t[row] /= get_num(row, row);
+    }
+
+    // Find for highest exponent
+    int highest = valid_point_num - 1;
+    for (; highest >= 0; highest++) {
+        if (!compare_double(t[highest], 0)) {
+            break;
+        }
+    }
+
+    printf("%d\n", highest);
+
+    // Evaluate
+    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;
+}