是否存在相等的差

题源

PTA 乙级

题解

#include<stdio.h>
int N;
int card[10001],num;
int box[10001] = {0};
int main(){
    scanf("%d",&N);
    int i = 0;
    for(i = 1;i <= N;i++){
        scanf("%d",&num);
        card[i] = num>i? num-i:i-num; 
        box[card[i]]++;
    }
    for(i = N;0 <= i;i--)if(box[i]>1)printf("%d %d\n",i,box[i]);
    getchar();getchar();
    return 0;
}