https://www.patest.cn/contests/pat-a-PRactise/1009

#include <cstdio>#include <iostream>#include <cstring>using namespace std;const int N = 1001;double a[N],b[N],c[2*N];int main() {	int n;	scanf("%d",&n);	int index;	double val;	for (int i = 0; i < n; i++) {		scanf("%d %lf",&index,&val);		a[index] = val;	}	scanf("%d",&n);	for (int i = 0; i < n; i++) {		scanf("%d %lf",&index,&val);		b[index] = val;	}	for (int i = 0; i < N; i++) {		for (int j = 0; j < N; j++) {			c[i+j] += a[i]*b[j];		}	}	int cnt = 0;	for (int i = 0; i < 2*N; i++) {		if (c[i]) cnt++;	}	printf("%d",cnt);	for (int i = 2*N - 1; i >= 0; i--) {		if (c[i]) printf(" %d %.1f",i,c[i]);//pay attention :double類型的數據輸入是%lf,輸出是%f	}	return 0;}