在O（1）的时间内计算n个整数落在区间[a,b]的个数

预处理时间为O（n+k)
算法导论第三版8.2-4题

int find_inverter_count(int *array,int length,int maximum,int inverter_left,int inverter_right)
{if(inverter_left<0 || inverter_right>maximum || inverter_right<inverter_left){perror("inverter error");return -1;}int *count_array = new int[maximum+1];for (int i = 0; i < maximum+1; ++i) {count_array[i] = 0;}for (int i = 0; i < length; ++i) {count_array[array[i]] = count_array[array[i]] + 1;}for (int i = 1; i < maximum+1; ++i) {count_array[i] = count_array[i] + count_array[i-1];}int count = 0;if(inverter_left == 0)count =  count_array[inverter_right];elsecount =  count_array[inverter_right] - count_array[inverter_left - 1];delete [] count_array;return count;
}