最大子段和（三种方法）

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给定n个整数（可能包含负数）组成的序列，求该序列子段和的最大值。

//暴力（三重循环）#include<stdio.h>#define n 6int main(){int i,j,k;int a[n] = {-2,11,-4,13,-5,-2};int tempsum,max = 0;int besti,bestj;for(i = 0;i < n;i ++){for(j = 0;j < n;j ++){tempsum = 0;for(k = i;k <= j;k ++)tempsum += a[k];if(tempsum > max){max = tempsum;besti = i;bestj = j;}}}printf("the best position is %d ~ %d,the max sum is %d.",besti + 1,bestj + 1,max);return 0;} ===========================================================================================//由三个循环变成两个循环的算法#include<stdio.h>#define n 6int main(){int i,j,k;int a[n] = {-2,11,-4,13,-5,-2};int tempsum,max = 0;int besti,bestj;for(i = 0;i < n;i ++){tempsum = 0;for(j = i;j < n;j ++){tempsum += a[j];if(tempsum > max){max = tempsum;besti = i;bestj = j;}}}printf("the best position is %d ~ %d,the max sum is %d.",besti + 1,bestj + 1,max);return 0;}=============================================================================================== //一次循环解决所有问题#include<stdio.h>#define n 6int main(){int i,j,k;int a[n] = {-2,11,-4,13,-5,-2};int besti,bestj;int sum = 0,b = 0;for(i = 0;i < n;i ++){if(b > 0)b += a[i];elseb = a[i];if(b > sum)sum = b; }printf("the best position is,the max sum is %d.",sum);return 0;}

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