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Fix: resolve unsigned loop bug in trapped rainwater implementation #3130

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Fix: resolve unsigned loop bug in trapped rainwater implementation #3130

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6 changes: 3 additions & 3 deletions dynamic_programming/trapped_rainwater.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ namespace dynamic_programming {
* @param heights Array representing the heights of walls
* @return The amount of trapped rainwater
*/
uint32_t trappedRainwater(const std::vector<uint32_t>& heights) {
uint64_t trappedRainwater(const std::vector<uint32_t>& heights) {
std::size_t n = heights.size();
if (n <= 2)
return 0; // No water can be trapped with less than 3 walls
Expand All @@ -39,12 +39,12 @@ uint32_t trappedRainwater(const std::vector<uint32_t>& heights) {

// Calculate the maximum height of wall to the right of each wall
rightMax[n - 1] = heights[n - 1];
for (std::size_t i = n - 2; i < n; --i) {
for (std::size_t i = n - 2; i != static_cast<std::size_t>(-1); --i) {
rightMax[i] = std::max(rightMax[i + 1], heights[i]);
}

// Calculate the trapped rainwater between walls
uint32_t trappedWater = 0;
uint64_t trappedWater = 0;
for (std::size_t i = 0; i < n; ++i) {
trappedWater +=
std::max(0u, std::min(leftMax[i], rightMax[i]) - heights[i]);
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