'commit'

TangDou/AcWing/HighPrecision/793_mul.cpp

@@ -0,0 +1,32 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 1e5 + 10;
+int a[N], al;
+int b[N], bl;
+void mul(int a[], int &al, int b[], int &bl) {
+    int t = 0;
+    int c[N] = {0};
+    for (int i = 0; i < al; i++)
+        for (int j = 0; j < bl; j++)
+            c[i + j] += a[i] * b[j];
+    al += bl;
+    for (int i = 0; i < al; i++) {
+        t += c[i];
+        a[i] = t % 10;
+        t /= 10;
+    }
+    // 前导0
+    while (al > 0 && a[al] == 0) al--;
+}
+
+int main() {
+    string x, y;
+    cin >> x >> y;
+    for (int i = x.size() - 1; i >= 0; i--) a[al++] = x[i] - '0';
+    for (int i = y.size() - 1; i >= 0; i--) b[bl++] = y[i] - '0';
+
+    mul(a, al, b, bl);
+    for (int i = al; i >= 0; i--) printf("%d", a[i]);
+    return 0;
+}