数组中出现次数超过一半的数字 代码(C)
本文地址: http://blog.csdn.net/caroline_wendy
题目: 数组中有一个数字出现的次数超过数组长度的一半, 请找出这个数字.
1. 使用高速排序(QuickSort)的方法, 把中值(middle)和索引(index)匹配, 输出中值, 并检測是否符合要求.
2. 使用计数方法依次比較.
代码:
方法1:
/* * main.cpp * * Created on: 2014.6.12 * Author: Spike */ /*eclipse cdt, gcc 4.8.1*/ #include <stdio.h> #include <stdlib.h> int RandomInRange(int min, int max) { int random = rand() % (max - min + 1) + min; return random; } void Swap(int* num1, int* num2) { int temp = *num1; *num1 = *num2; *num2 = temp; } int Partition(int data[], int length, int start, int end) { if(data == NULL || length <= 0 || start < 0 || end >= length) { return -1; } int index = RandomInRange(start, end); Swap(&data[index], &data[end]); int small = start - 1; for(index = start; index < end; ++ index) { if(data[index] < data[end]) { ++ small; if(small != index) Swap(&data[index], &data[small]); } } ++ small; Swap(&data[small], &data[end]); return small; } bool CheckMoreThanHalf (int* numbers, int length, int number) { int times = 0; for (int i=0; i<length; ++i) { if (numbers[i] == number) ++times; } if (times*2 <= length) { return false; } return true; } int MoreThanHalfNum(int* numbers, int length) { if (numbers == NULL || length <= 0) return 0; int middle = length >> 1; int start = 0; int end = length-1; int index = Partition(numbers, length, start, end); while (index != middle) { if (index > middle) { //前面部分的数字多 end = index-1; index = Partition(numbers, length, start, end); } else { start = index+1; index = Partition(numbers, length, index+1, start); } } int result = numbers[middle]; if (!CheckMoreThanHalf(numbers, length, result)) return 0; return result; } int main(void) { int str[] = {1, 2, 3, 4, 4, 4, 5, 4, 4}; int result = MoreThanHalfNum(str, 9); printf("reuslt = %d\n", result); return 0; }
方法2:
/* * main.cpp * * Created on: 2014.6.12 * Author: Spike */ /*eclipse cdt, gcc 4.8.1*/ #include <stdio.h> #include <stdlib.h> bool CheckMoreThanHalf (int* numbers, int length, int number) { int times = 0; for (int i=0; i<length; ++i) { if (numbers[i] == number) times++; } if (times*2 < length) return false; return true; } int MoreThanHalfNum (int* numbers, int length) { if (numbers == NULL || length <= 0) return 0; int result = numbers[0]; int times = 1; for (int i=0; i<length; ++i) { if (times == 0) { result = numbers[i]; times = 1; } if (numbers[i] == result) times++; else times--; } if (!CheckMoreThanHalf(numbers, length, result)) return 0; return result; } int main(void) { int str[] = {1, 2, 3, 2, 2, 2, 5, 2, 4}; int result = MoreThanHalfNum(str, 9); printf("reuslt = %d\n", result); return 0; }
输出:
reuslt = 4
时间: 2024-10-19 06:18:11