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public/c/ch2/bigcheng/bigchengold.c

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+#include <stdio.h>
+#include <string.h>
+#define MAX_LEN 1000
+// 计算两个大整数的乘积
+void multiply(const char* a, const char* b, char* result) {
+    int lenA = strlen(a), lenB = strlen(b), lenResult = lenA + lenB;
+    int arr[MAX_LEN * 2] = {0};
+
+    // 进行乘法运算
+    for (int i = 0; i < lenA; ++i)
+        for (int j = 0; j < lenB; ++j)
+            arr[i + j] += (a[lenA - i - 1] - '0') * (b[lenB - j - 1] - '0');
+    // 处理进位
+    for (int i = 0; i < lenResult - 1; ++i) {
+        arr[i + 1] += arr[i] / 10;
+        arr[i] %= 10;
+    }    
+    // 构建结果字符串
+    int index = 0;
+    while (index < lenResult && arr[index] == 0) ++index;
+    if (index == lenResult) strcpy(result, "0");
+    else {
+        for (int i = index; i < lenResult; ++i)
+            result[i - index] = arr[lenResult - i - 1] + '0';
+        result[lenResult - index] = '\0';
+    }
+}
+
+int main() {
+    char a[MAX_LEN + 1], b[MAX_LEN + 1], result[MAX_LEN * 2 + 1];
+    printf("输入第一个大整数: ");
+    scanf("%s", a);
+    printf("输入第二个大整数: ");
+    scanf("%s", b);
+    multiply(a, b, result);
+    printf("结果: %s\n", result);
+    return 0;
+}