51nod 1215 width of the array &poj 2796 feel Good (monotonic stack)

　　The monotone stack is the classic operation of which interval is the most value for each number.

Throw the number one into the monotone stack, when it pops up [st[top-1]+1,i-1] This interval is the number that pops up to be the most-valued interval.

poj2796 pop up when the answer can be updated

#include <iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<algorithm>#include<queue>#include<cmath>#include<map>#definell Long Longusing namespacestd;Const intmaxn=500010, inf=1e9;intn,top,ansl,ansr;ll ans=-1;intSt[maxn],a[maxn];ll SUM[MAXN];voidReadint&k) {    intf=1; k=0;CharC=GetChar ();  while(c<'0'|| C>'9') c=='-'&& (f=-1), c=GetChar ();  while(c<='9'&&c>='0') k=k*Ten+c-'0', c=GetChar (); K*=F;}intMain () {read (n);  for(intI=1; i<=n;i++) read (A[i]), sum[i]=sum[i-1]+a[i];a[++n]=-1;  for(intI=1; i<=n;i++)    {         for(; top&&a[i]<=a[st[top]];top--) {ll Val=1ll*a[st[top]]* (sum[i-1]-sum[st[top-1]]); if(Val>ans) ans=val,ansl=st[top-1]+1, ansr=i-1; } st[++top]=i; } printf ("%lld\n%d%d", ANS,ANSL,ANSR); return 0;}

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51nod1215 the sum of the contribution of the maximal value to the answer and the contribution of the minimum value to the answer.

　　Obvious contribution for a[i]* (I-st[top]) * (st1[top]-st[top-1]);

#include <iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<algorithm>#include<queue>#include<cmath>#include<map>#definell Long Longusing namespacestd;Const intmaxn=500010, inf=1e9;intN,top1,top2;inta[maxn],b[maxn],st1[maxn],st2[maxn];ll mx,mn;voidReadint&k) {    intf=1; k=0;CharC=GetChar ();  while(c<'0'|| C>'9') c=='-'&& (f=-1), c=GetChar ();  while(c<='9'&&c>='0') k=k*Ten+c-'0', c=GetChar (); K*=F;}intMain () {read (n);  for(intI=1; i<=n;i++) read (A[i]), b[i]=a[i];b[++n]=inf;  for(intI=1; i<=n;i++)    {         for(; top1&&a[i]<=a[st1[top1]];top1--) MN+=1ll*a[st1[top1]]* (I-ST1[TOP1]) * (st1[top1]-st1[top1-1]);  for(; top2&&b[i]>=b[st2[top2]];top2--) MX+=1ll*b[st2[top2]]* (I-ST2[TOP2]) * (st2[top2]-st2[top2-1]); st1[++top1]=st2[++top2]=i; } printf ("%lld\n", mx-mn); return 0;}

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51nod 1215 width of the array &poj 2796 feel Good (monotonic stack)