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+#!perl
+use strict;
+use warnings FATAL => qw(all);
+
+=prompt
+You are given an array of altitude gain.
+Write a script to find the peak point gained.
+
+Example 1
+
+Input: @gain = (-5, 1, 5, -9, 2)
+Output: 1
+
+start: 0
+1st change:  0 + (-5) = -5
+2nd change: -5 + 1    = -4
+3rd change: -4 + 5    = 1
+4th change:  1 + (-9) = -8
+5th change: -8 + 2    = -6
+
+max(0, -5, -4, 1, -8, -6) = 1
+
+
+Example 2
+
+Input: @gain = (10, 10, 10, -25)
+Output: 30
+
+start: 0
+1st change:  0 + 10    = 10
+2nd change: 10 + 10    = 20
+3rd change: 20 + 10    = 30
+4th change: 30 + (-25) = 5
+
+max(0, 10, 20, 30, 5) = 30
+
+
+Example 3
+
+Input: @gain = (3, -4, 2, 5, -6, 1)
+Output: 6
+
+start: 0
+1st change:  0 + 3    = 3
+2nd change:  3 + (-4) = -1
+3rd change: -1 + 2    = 1
+4th change:  1 + 5    = 6
+5th change:  6 + (-6) = 0
+6th change:  0 + 1    = 1
+
+max(0, 3, -1, 1, 6, 0, 1) = 6
+
+
+Example 4
+
+Input: @gain = (-1, -2, -3, -4)
+Output: 0
+
+start: 0
+1st change:  0 + (-1) = -1
+2nd change: -1 + (-2) = -3
+3rd change: -3 + (-3) = -6
+4th change: -6 + (-4) = -10
+
+max(0, -1, -3, -6, -10) = 0
+
+
+Example 5
+
+Input: @gain = (-10, 15, 5)
+Output: 10
+
+start: 0
+1st change:   0 + (-10) = -10
+2nd change: -10 + 15    = 5
+3rd change:   5 + 5     = 10
+
+max(0, -10, 5, 10) = 10
+
+=cut
+
+use Test2::V0 -no_srand => 1;
+
+is(peak_point(-5, 1, 5, -9, 2), 1, 'Example 1');
+is(peak_point(10, 10, 10, -25), 30, 'Example 2');
+is(peak_point(3, -4, 2, 5, -6, 1), 6, 'Example 3');
+is(peak_point(-1, -2, -3, -4), 0, 'Example 4');
+is(peak_point(-10, 15, 5), 10, 'Example 5');
+done_testing();
+
+sub peak_point
+{
+     my @arr = @_;
+     my $sum;
+     my $max = 0;
+     for my $elm ( @arr )
+     {
+          $sum += $elm;
+          $max = $max > $sum ? $max : $sum;
+     }
+     return $max;
+}