the algorithm of three version below is essentially the same, namely, Kadane’s algorithm, which is of O(n) complexity. https://en.wikipedia.org/wiki/Maximum_subarray_problem
the evolution of the implementations is to remove redundancy and do what is really needed, the side effect of doing so is becoming more efficient.
IMHO, version 1.0.2 is well commented which shows the guidelines of efficient bookkeeping of boundaries, first and last can also be easily changed to first_iter and last_iter to print the whole subarray if needed.
// version 1.0.0, a coordinate array, a traversing to find the first element
#include <cstdio>
#include <algorithm>
#define MAXSIZE 10005
int main() {
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
#endif
int N,i,tmp,*p;
int nums[MAXSIZE]={-1}, dp[MAXSIZE]={0};
while(scanf("%d",&N)==1 && N>0) {
for(i=1;i<=N;++i) { scanf("%d",&nums[i]); }
for(i=1;i<=N;++i) {
tmp=nums[i]+(dp[i-1]>0?dp[i-1]:0);
dp[i]=tmp>0?tmp:0;
//dp[i]=std:max(0,nums[i]+std::max(dp[i-1],0));
}
p=std::max_element(dp,dp+N+1);
if(p==dp) {
if(nums==std::max_element(nums,nums+N+1)) { i=1,tmp=N; }
else {
for(i=0;i<=N && nums[++i]<0;) {}
for(tmp=i;nums[++tmp]==0;) {} --tmp;
}
}
else {
for(tmp=i=p-dp;i>0 && dp[--i]>0;) {}
for(;i>0 && nums[i]==0 && dp[--i]==0;) {} ++i;
}
printf("%d %d %d\n",*p,nums[i],nums[tmp]);
}
return 0;
}// version 1.0.1, no coordinate array, modifying the data, a traversing to find first element
#include <cstdio>
#include <algorithm>
#define MAXSIZE 10005
int main() {
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
#endif
int N,i,j,tmp,last,sum;
int nums[MAXSIZE]={-1};
while(scanf("%d",&N)==1 && N>0) {
for(i=1;i<=N;++i) { scanf("%d",&nums[i]); }
for(sum=-1,last=nums[N],j=0, i=1;i<=N;++i) {
tmp=nums[i]+(nums[i-1]>0?nums[i-1]:0);
if(tmp>=0) {
if(tmp>sum) { sum=tmp; last=nums[i]; j=i; }
nums[i]=tmp;
}
}
if(sum==-1) ++sum;
else for(;j>0 && nums[--j]>=0;) {}
printf("%d %d %d\n",sum,nums[j+1],last);
}
return 0;
}// version 1.0.2, no coordinate array, not modify data, no extra traversing to find boundary element
#include <cstdio>
#include <algorithm>
#define MAXSIZE 10005
int main() {
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
#endif
// prev -- maxsum ending here, sum -- maxsum so far, res -- result
int N,i,first,last,tmp,sum,res,prev;
int nums[MAXSIZE];
while(scanf("%d",&N)==1 && N>0) {
for(i=0;i<N;++i) { scanf("%d",&nums[i]); }
for(res=prev=sum=-1,first=nums[0],last=nums[N-1], i=0;i<N;++i) {
if(prev<0) {
if(nums[i]>=0) {
// prev start increasing, update candidate of first -- tmp
tmp=prev=nums[i];
// update candidate of result -- sum
if(prev>sum) { sum=prev; }
}
}
else {
prev+=nums[i];
// prev stop increasing, update first, last, res
if(nums[i]<=0) { if(sum>res) { res=sum; first=tmp; last=nums[i-1]; } }
// update candidate of result -- sum
else if(prev>sum) { sum=prev; }
}
}
// update first, last, res, -- only if partial sum remain increasing
if(sum>res) { res=sum; first=tmp; last=nums[i-1]; }
// all negative
if(res==-1) ++res;
printf("%d %d %d\n",res,first,last);
}
return 0;
}版权声明：本文为博主原创文章，未经博主允许不得转载。// p.s. If in any way improment can be achieved, better performance or whatever, it will be well-appreciated to let me know, thanks in advance.