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public class TrappingRainWater {
public int trap(int[] height) {
if (height == null || height.length < 3) {
return 0;
}
int[] maxl = new int[height.length];
int[] maxr = new int[height.length];
int maxlv = height[0];
int maxrv = height[height.length - 1];
for (int i = 1; i < height.length - 1; i++) {
maxl[i] = maxlv;
maxlv = Math.max(maxlv, height[i]);
int t = height.length - i - 1;
maxr[t] = maxrv;
maxrv = Math.max(maxrv, height[t]);
}
int result = 0;
for (int i = 1; i < height.length - 1; i++) {
int crt = Math.min(maxl[i], maxr[i]) - height[i];
result += Math.max(0, crt);
}
return result;
}
}
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