A1037

本題思路正確，注意點：出現段錯誤可能原因：
1、數組給小了
2、數組下標超出數組大小了

#include<cstdio>
#include<cstdlib>
#include<string.h>
#include<math.h>
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<string>
#include<algorithm>
using namespace std;
const int maxn=100010;
int c[maxn],p[maxn];
bool cmp(int a,int b){
	return a>b;
}
int main(){
	#ifdef ONLINE_JUDGE
	#else
		freopen("1.txt","r",stdin);
	#endif
	int nc,np;
	long long sum=0;
	scanf("%d",&nc);
	for(int i=1;i<=nc;i++){
		scanf("%d",&c[i]);
	}
	scanf("%d",&np);
	for(int i=1;i<=np;i++){
		scanf("%d",&p[i]);
	}
	sort(c+1,c+nc+1,cmp);
	sort(p+1,p+np+1,cmp);
	if((c[nc]>=0&&p[1]<=0)||(c[1]<=0&&p[np]>=0)){
		printf("0");
		return 0;
	}
	//正數相乘
	int m=1,n=1;
	while(c[m]>0&&p[n]>0){
		sum+=(long long)(c[m]*p[n]);
		m++;
		n++;
	}
	while(c[m]>=0&&m<=nc){                            //之前遺漏了m<=nc的判斷，以致於出現了數組下標越界的情況，報段錯誤 
		m++;
	}
	while(p[n]>=0&&n<=np){							  //之前遺漏了n<=np的判斷，以致於出現了數組下標越界的情況，報段錯誤 
		n++;
	}
	while(nc>=m&&np>=n){
		sum+=(long long)(c[nc]*p[np]);
		nc--;
		np--;
	}
	printf("%lld",sum);
	return 0;
}

算法筆記中比較簡潔明瞭的寫法（值得學習：兩個while循環）：

#include<cstdio>
#include<cstdlib>
#include<string.h>
#include<math.h>
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<string>
#include<algorithm>
using namespace std;
const int maxn=100010;
int c[maxn],p[maxn];
bool cmp(int a,int b){
	return a>b;
}
int main(){
	#ifdef ONLINE_JUDGE
	#else
		freopen("1.txt","r",stdin);
	#endif
	int nc,np;
	long long sum=0;
	scanf("%d",&nc);
	for(int i=1;i<=nc;i++){
		scanf("%d",&c[i]);
	}
	scanf("%d",&np);
	for(int i=1;i<=np;i++){
		scanf("%d",&p[i]);
	}
	sort(c+1,c+nc+1,cmp);
	sort(p+1,p+np+1,cmp);
	int m=1,n=1;
	while(m<=nc&&n<=np&&c[m]>0&&p[n]>0){
		sum+=c[m]*p[n];
		m++;
		n++;
	} 
	m=nc,n=np;
	while(m>=1&&n>=1&&c[m]<0&&p[n]<0){
		sum+=c[m]*p[n];
		m--;
		n--;
	}
	printf("%lld",sum);
	return 0;
}