求最大子数组和的6个版本

#include <stdio.h>#define INF ( (1 << 30) - 1 )#define SIZE 100int maxSubArrayV1(int array[], int size){int maxSum = -INF;int start, end;for (start = 0; start < size; start++)for (end = start; end < size; end++){//sum中很多数组元素值重复计算，可优化int sum = 0;int i;for (i = start; i <= end; i++)sum += array[i];if (sum > maxSum)maxSum = sum;}return maxSum;}int maxSubArrayV2(int array[], int size){int maxSum = -INF;int start, end;for (start = 0; start < size; start++){//sum用来保存上次计算的和，每次只需加上新的数组元素值int sum = 0;for (end = start; end < size; end++){sum += array[end];if (sum > maxSum)maxSum = sum;}}return maxSum;}int maxSubCrossingArray(int array[], int first, int center, int last){int leftMaxSum = -INF;int sum = 0;int i;for (i = center; i >= first; i--){sum += array[i];if (sum > leftMaxSum)leftMaxSum = sum;}int rightMaxSum = -INF;for (i = center + 1; i <= first; i++){sum += array[i];if (sum > rightMaxSum)rightMaxSum = sum;}return leftMaxSum + rightMaxSum;}int maxSubArrayV3(int array[], int first, int last){if (first == last)return array[first] > 0 ? array[first] : 0;int center = (first + last) >> 1;//分治int leftMaxSum = maxSubArrayV3(array, first, center);int rightMaxSum = maxSubArrayV3(array, center + 1, last);int maxSum = maxSubCrossingArray(array, first, center, last);if (leftMaxSum > maxSum)maxSum = leftMaxSum;if (rightMaxSum > maxSum)maxSum = rightMaxSum;return maxSum;}int maxSubArrayV4(int array[], int size){//maxSumWithTail[tail]表示以元素array[tail]为结尾的最大字数组的和//分两种情况：1.元素array[tail]和tail之前的元素组成最大字数组。2.元素array[tail]单独作为最大字数组int maxSumWithTail[SIZE];maxSumWithTail[0] = array[0] > 0 ? array[0] : 0;int maxSum = maxSumWithTail[0];int tail;for (tail = 1; tail < size; tail++){//每回只应用元素maxSumWithTail[tail - 1]，所以maxSumWithTail可优化if (maxSumWithTail[tail - 1] > 0)maxSumWithTail[tail] = array[tail] + maxSumWithTail[tail - 1];elsemaxSumWithTail[tail] = array[tail];if (maxSumWithTail[tail] > maxSum)maxSum = maxSumWithTail[tail];}return maxSum;}int maxSubArrayV5(int array[], int size){int maxSum = 0;int maxSumWithTail = 0;int tail;for (tail = 0; tail < size; tail++){if (maxSumWithTail > 0)maxSumWithTail += array[tail];elsemaxSumWithTail = array[tail];if (maxSumWithTail > maxSum)maxSum = maxSumWithTail;}return maxSum;}int maxSubArrayV6(int array[], int size){int maxSum = -INF;int tempMaxSum = 0;int i;for (i = 0; i < size; i++){tempMaxSum += array[i];if (tempMaxSum > maxSum)maxSum = tempMaxSum;if (tempMaxSum < 0)tempMaxSum = 0;//当tmpMaxSum > 0时，tmpMaxSum有潜力成为最大字数组和}return maxSum;}int main(){return 0;}